Help - I'm not agreeing with the catch equation

Can you help - I'm using https://pokemongo.gamepress.gg/catchcalc#/ to calculate the chance of catching a level 1 Dragonite with a normal pokeball and no throw bonus'

This is my comment from
https://www.reddit.com/r/TheSilphRoad/comments/7lip92/question_do_all_lvl_1_pokemon_have_a_100_catch/drnssdt/

Dragonite 5% BCR, at level 1: 2*CPM = 0.188. No throw bonus'

So, 1-(1-(0.05/0.188)) = (0.05/0.188) = 0.26595... = 27% but the on-site calculator gives a 15% chance of catch per throw... am I missing something?