I haven't tried, but normally it's open to interpretation, whether a number is positive or not.

A5 uses a fixpoint format, I think it was 22.10

This means we have a size of 4 byte, this is 32 bits.
The last 10 (1024 combinations, makes 3 decimal places) bits are taken for the positions after the decimal point, the remaining 22 bits are used for the positions before the decimal point.
With this format, we can store numbers, but there is no informations about the sign yet.
To get negatvie and positive numbers, the highest bit is used. A 1 means negatvie number, a 0 means negative number.

You might think we lose a lot of place with this as we only have 21 (2097152 combinations) instead of 22 (4194304) bits. That is not true. In fact we only moved the area where we can store numbers. We can't use that high positive nubmers anymore, therefore we can store negative numbers. It's all a question of interpretation.

(The fixpoint format of A5/6 might differ from 22.10, I don't know it out of my mind right now. The idea behind it is the same, it only changes the maximum number sizes/precision before and behind the decimal point. Maybe Conitec also uses some of the leading bits as variable flags like the info flag, I guess you will have to ask Conitec about that for more details)