For instance, if I shrink an outline whose size is 1027 by 100 units, the info box value already has a comma. The input value therefore becomes 1,027-100 and the resulting outline becomes -99 (-99 beyond the scale origin point). The original value with comma seems to be invalidated or understood to be 1,027 in German sense (as a decimal separator).
I don’t think a thousand separator is unnecessary in these values whose digits are not typically expected to be multiple groups of three digits like million anyway.