What does at least and at most mean?

At least means the minimum or the lowest baseline.

For example: A candy bar costs between 1-2$  so if there is a boy asking money from his mom, he needs to ask for at least 1$

At most means the maximum amount or the highest amount or ceiling amount. 

For example: To buy a shirt online, I need at least $10 but at most, it should cost $25

Bi’m pretty sure hope it works