Rashi on Exodus 5:18/רש"י על שמות ה׳:י״ח

1ותכן לבנים means THE NUMBER OF THE BRICKS; similar is (2 Kings 12:12) “the money המתכן”, i. e. the money which was counted, just as it states in that passage (v. 11), “and they put it up in bags and counted the money”.