Normies get taught % at school. They might have siblings and have to divide things up. They will get salary raises in % perhaps. Maybe involved with a small business and accounts, growth of sales in %. Bombarded with % in news, weather. [which they may not understand, I guess].
Comments
2-5% = hardly any
~20% = a few
50% = half
70-80% = lots
90%+ = almost all
So they probably bot overestimate the proportion of trans etc but also provide an imprecise description of their view