The wiki article is referring to the first play in the list (your Top Ranks), and not your first play on the map.
Looking at your Top Ranks, if you were to get a score worth 51pp, even if it took you 100 tries, that score would become the first play in your Top Ranks and would be weighted 100%.
Even with that said, you would still not get 51pp for that play because all of the scores below it are now weighted less, and thus, would be worth less.