It's rounding the field, so the resulting calculation is not correct.
We only work with quarter hours (1.00, 1.15, 1.30, 1.45).
I was incorrect above, it will still round if a half figure is input (1.5).
The field is set to General Number and the decimal is auto.
I've tried changing to Set Number with 2 decimal places, but its still rounding.
I'm sure its something obvious ... (but not to me)