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'.”
(..) Then tell him that I've threatened your life, unless you help me to get across the border. Tell him that for half the sum of the reward, plus a forged pass to get you out of the country, you will deliver me into an ambush at some prenamed place... of the Fat Man's choosing (..)1975 The Return of the Pink Panther