He started off with 32 packs of buns each with 12 buns in it. To start you would do 32 x 12 which gives you 384. After the picnic there were 2 full packages of buns which each have 12 buns in them and another 5 buns. So those 2 packs and the extra would give you 29 buns. You would then take the original amount he started with and take away 29 giving you 355.
