SUM not calculating rght

Good day

ROUND(SUM(Valid Bet Amount), 2) AS TotalBetAmount,

Im using the code above but the query outcome is not right. i have negative and positive value in my column Valid Bet Amount but, when i tried to compare it to our back end its not tally. our backend show -1000 but my query will show 13400?

Can anyone help me to fix this problem? i even compare my data in excel. the excel get it right but my query not. thank you vert much

What data type is Valid Bet Amount (I presume you have got that field name in back-ticks?)

It should probably be DECIMAL(10,2) or similar - if you're using DECIMAL or FLOAT then you will get rounding errors which could mount up quite significantly if your table has a lot of rows.