Specifying desired file size in kilobytes / decimals instead of megabytes?

[MediocreJames]

Hello,

I encode a lot of tiny video clips for archiving purposes and I am interested in knowing whether it is possible to enter the desired file size in kilobytes or decimals instead of megabytes?
Usually I use HEVC (x265) codec and Two-pass file size option. In some cases the resulting file size is a little bit larger than the target file size. For example, if I set it to 5MB the result is something like 5,01 or 5,03. I could just solve this by lowering the file size to something like 4,9MB, but it doesn't seem to be possible. As it is right now I have to set the file size to 4MB instead. I realize that the difference in quality is very minimal or just completely negligible, but I just can't help, but wonder whether it's possible or not.