Working odd summer jobs has been 'the sum of' my experience so far. [=has been all the experience I've had so far]
That picture 'sums' him 'up' perfectly. [=that picture perfectly shows what kind of person he is]
“So, you don't want to go because you think it will be boring?” “That just about 'sums it up'.”
(..) Okay, let it go. - Was good, wasn't it ? - Quite nice. That's excellent, son. (Rose) Mr Andrews, forgive me... l did the sum in my head... With the number of lifeboats times the capacity you mentioned... ..it seems there are not enough for everyone. About half, actually. (..)1997 Titanic