for all that; considering that; unexpectedly
Used to express that something is contrary to what one would expect given the circumstances. Often follows a clause describing a situation, and the main clause states a surprising or disproportionate result.
彼はあまり勉強しなかった。その割には試験の点がよかった。
He didn't study much. Considering that, his exam score was good.
このレストランは安い。その割には料理がおいしい
This restaurant is cheap. For all that, the food is delicious.
Phrase composed of その (that) + 割 (proportion, rate) + に (particle) + は (topic marker). Literally 'in that proportion', it developed into a conjunction meaning 'considering that'.