Hacker News Reader

That's not an error, it's what 5 Guys advertise. It's the number of combinations for their toppings.

That sounds like an error to me. "Number of toppings" is not the same as "Number of possible combinations of toppings".

Shouldn’t it be a lot more? Around 20 toppings in any combination and count would be 20! + 19! + 18! … no?

2^20

Does order of toppings matter?

yes, only a monster would put the pickles underneath the tomato