Multiple location sites are really only a "special case" of many sites which cover more than a single building in that there are gaps between their defined boundaries. But a site with 6 separate locations and say, a town, with a number of streets and districts both raise the same question of how many of the locations/districts/streets/buildings "need" to have been seen. It surely depends on whether the other "locations" etc really "add" anything or whether they are just "more of the same". And even single buildings have "multiple rooms" – How many rooms does one have to "see" to see 100% of Versailles! And with Natural Sites the problem is worse – what about multiple trails, mountains, lakes etc etc.
And all sites have an "experiential" aspect to visiting them which varies according to a very wide range of factors which can add to or detract from the value of what you "see". What if I go to the Okapi reserve and don't see an Okapi - 0% or 100%??? What if it is raining and I don't get the great view of somewhere, or if a significant aspect is closed on the day I visit, or we are there with a particularly good guide, or my viewing experience is ruined by a great clamour of school kids as I was going round, or I had a bad headache....... etc etc in reductio ad absurdam!!
And even if I do "See" it - one man's "See" is another man's "Missed all the nuances and interesting bits....." For instance I fully accept that I am not good at "seeing" Gothic cathedrals – I walk round and think "well it's certainly big" and then move on. If only I could really appreciate them – I know others get far more out of them than I do!
For these sorts of reasons I don't favour the "mathematical approach" but prefer the "qualitative" which inevitably has to be "personal" and not comparable across individuals. So I count a site as "seen" if I "see" ANY part of it and get that "simple count" issue out of the way. Whether I count it in my mind as "seen" is another matter altogether as I then take into account the sort of factors mentioned above. If I want to go back again then perhaps I can't have fully "seen" it! (Idea - perhaps I should have a list of Sites "I want to go back to"!! But then I need to balance these against "Sites I haven't yet seen but want to"!) In any case there will be things I don't realise I "saw" until I get back and do a bit of study and discover the significance of something possibly quite minor. That is why prior study is a help to avoid the situation of getting home and discovering that you missed something significant- which means it can't fully be counted as "seen" in your mind! But then I don't know what I don't know and might be missing all sorts of things on that basis - and I change over time as well and "see" different things so perhaps the true answer is that no site can ever be ticked off as "seen"!
3 stories (Not WHS related but still apposite I think)
a. We had just "seen" our first Polar bear in Svalbard – a brownish white "object" at 3 miles through binoculars from our boat which must have been a bear as it seemed to be moving . We all sat round and discussed whether, if that was the only one we got on the trip, would we have "seen" Polar bear. Later we had an hour following by boat at 20 metres a mother and 2 cubs "doing" what Polar bears generally "do" – not a great deal but generally behaving quite "bearlike"! We were pretty pleased. That evening our guide showed us photos of a number of Polar Bears tearing the flesh off a whale – who had "seen" Polar Bear?
b. In the Amazon forest an American millionaire was trying to "see" 1000 bird species in a year – he had a professional guide with tapes of bird calls and played one near us – out came a Goeldi's Antbird. Within 30 seconds the bird had been ticked and the pair moved on to the next on their list. At the same place was a guy studying Ant birds for a year. Who was "seeing" them?
c. In a small and frankly, undistinguished, Vermont town I asked where was the best place round there to go to see the "Fall scenery" - I was going to give it about half an hour - I mean, how long can you spend looking at orange leaves! ... "Man you could burn up a whole life here and still not see everything" was the reply. I was put in my place! | 
