Poker is the a-x rule by phil goddam mathematically correct since it would mean raising UTG with a8...........?

On FTP academy lesson phil has a video explaining a-x rule being if you have an ace the kicker must be as many or more than the amount of player still to act for your hand to be 50/50 of winning the pot........ Is his math correct thought beucause firstly it seems wrong and secondly I can't understand how if your playing against 3 players how a2 would mean you aren't a 50:50 chance to win the hand.... I mean thinking about it there are only 3 aces left in the deck and that's 3/50= 6/100=6% which I thought meant mathematically u rthe only one with the ace...? Please correct my math if I'm wrong