Double entry book keeping Question

Hello Sir, on the revision kit of Kaplan there is this question which does not make sense to me, please could you help me understand it: Sasha has prepared a draft stattement of profit and loss for her business as follows: Sales 256,800 Cost of sales: Opening inventory: 13,400 Purchases 145,000 closing inventory (14,200) (144,200) Gross profit 112,600 Expenses (76,000) Net Profit 36,600 Sasha has not yet included the following items carriage in of £2300 discount recieved of £3900 carriage out of £1950 We need to adjust for these and find the new figure for gross and net profit. The answer as per the kit is gross profit at 110300 and net profit as 36250. However my question is why they would reduce the gross profit with carriage inward as it is income it should increase it right? also they adjusted discount received after the gross profit not along with purchases I dont understand that either as discount received must be part of the the purchases so should be considered all together? Please help me. thank you