E-book Viewer shows series index as arabic numerals but not always

In the viewer, if I click on "Show book metadata" the series index is shown as 177.5 if it is not an integer number but as CLXXVII if the index is 177.
I realize, that the Roman number system had no concept of a decimal point, it only handled fractions. 1/2 would be S so 177.5 would be CLXXVIIS in Roman Numerals.
I do not think anybody implemented proper conversion of decimal numbers into proper Roman Numerals.
I would like all numbers to show up equally, so I would like to know, whether there is a way to have all Numbers with Arabic Numerals even for Integers.

I searched the viewer forum for "roman numerals" and "series index" and found nothing.

Thanks in advance for your help.