％？
When something says '20% more volume,' don't you just reach for it?
Literal
20% volume-increase [quotative-って] written [when-と] unintentionally hand [subject-が] doesn't-come-out?
The question is a classic Japanese 'negative rhetorical' — 出ない？ asks 'doesn't your hand come out?,' which expects agreement with the positive statement 'yes, it does.' English uses the same trick ('don't you just love...?'). つい 'unintentionally, without meaning to' collocates with 手が出る ('to reach for, to give in to temptation') — the combination captures the impulse of grabbing something despite yourself. って is the casual topic/quotative particle, here taking the preceding phrase as a quoted label.