Understand how Bitfinex calculates transactions?

By adding all of my transactions that the API returns, I can not find the result that I have in my balance. Example with IOTA: My balance is 281.64315651000 IOTA (return by /v1/balances) List of transactions (return by /v1/mytrades): [ {"Price": "0.0002993", "amount", "79.28790511", "timestamp", "1513796864.0", "type": "Buy", "fee_currency": "BTC", "fee_amount": "- 0.00002373" "tid": 133864150, "order_id": 6341795236}, {"Price": "0.0002993", "amount", "202.43439879", "timestamp", "1513796835.0", "type": "Buy", "fee_currency": "BTC", "fee_amount": "- 0.00006059" "tid": 133862789, "order_id": 6341795236} , {"Price": "0.0002201", "amount", "232.99614795", "timestamp", "1513617498.0", "type": "Sell," "fee_currency": "BTC", "fee_amount": "- 0.00005128" "tid": 129555018, "order_id": 6274176492}, {"Price": "0.000191", "amount", "233.22973822", "timestamp", "1513439162.0", "type": "Buy", "fee_currency": "BTC", "fee_amount": "- 0.00004455" "tid": 126976949, "order_id": 6203768149} ] The result of all amount is : 281,95589417000 IOTA When sub fee : 281,67254723065 IOTA (my cacul for fee is fee_amount/price) So the balance and the result of transaction are different of 0,02939072065 IOTA How find the exactly balance with transaction ?