Form some reason if I try to multiply or divide I get error however addition and subtraction works fine. What am i doing wrong?

Form some reason if I try to multiply or divide I get error however addition and subtraction works fine. What am i doing wrong?

Try wrapping them in a VALUE() function:
VALUE({Hold}) * VALUE({Dosage})
INT() will do the same thing, but returns an integer rather than a float.
Bit more info on this thread
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