Invalid Calculation Value

My grid i created 2 accumulated field(stock balance(in) and stock balance(out) to accumulate value from “purchased qty” and “issued qty” and i create onrecord event to display the sum of the 2 accumulated field value and display on new field called “stock balance”.But the output totally wrong. please kindly advice.

onrecord event formula = {Stock Balance} = {Stock Balance(IN)} + {Stock Balance(OUT)};

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