you dont add up breakers to get total draw.
doesnt work like that.
you have power to play with, but out of space for new breakers it appears.
looks like a 6 circuit panel to me
you have 140 worth of breakers 70 on each pole that dont mean your maxxxxxxed but make sure you over count your loads on each line to be safe.........
and so you know its the top & bottem from each side & the middle from the other side thats on the same line.....
the way its set up now line 1 is 30-20-20 then line 2 = 20-30-20
So at the main service panel there is a 100 amp breaker which feeds this sub panel, if you exceed the breakers capacity it will trip. If it doesn't trip your ok.
You can also add up your simultaneous loads on this sub panel.