thats about the size of it

Thats about the size of it is an expression used when you want to say that is the way it is, or that someone has done or said something you agree with and want to reassure them they are correct about it. This usually pertains to the way something is or the way a situation typically goes; by saying thats about the size of it, they mean to agree with you that it is a pretty typical way it usually goes in this particular occurrence.