"%" signifies that a binary number follows, e.g. %10 would evaluate as decimal 2; "$" signifies that a hexadecimal number follows (hex for short), e.g. $02 evaluates as decimal 2.
For single-byte (8-bit) numbers, a binary number has 8 digits, each of which can have a value of 0 or 1. These can represent decimal numbers between 0 and 255. These bit-values are often used to represent the existance or absence of a condition. For instance, if they were used to represent the presence or absence of filters which could be used in conjunction (I know you say these cannot be), then %00100001 could indicate that the "zero"th filter and the fifth filter were simultaneously in place.
A single-byte hex number has two "digits", which can have values of 0-9 and A-F, where "A" represents 10, "B" is 11, and so on, with "F" equal to 15. This two-digit hex number also can represent decimal values between 0 and 255. The two digits of a hex number are sometimes referred to as "nibbles" (4 bits). %1111 is equivalent to $F and equals decimal 15. To calculate the decimal value of a hex number you multiply the decimal value of the high-order nibble by 16 and add the decimal value of the low-order nibble. For example, $EB equals 14*16 + 11, or 235.
Frequently (and this is the case with your values), the decimal value of a number represented in hex has no obvious significance. For instance, your value of $C0 is 192, which has no significance which refers to filters. But when looked at as a bit pattern, %11000000 might well be significant relative to %10000000.
To me, from the way you describe your equipment, the designer could have made the results you are looking for much more obvious by just returning a value between 0 and 6. There are probably historical reasons for the values actually returned, and they may have to do with setups which could potentially be much more complex--for example, perhaps there was equipment on which multiple filters could be used. It is also possible that the filters which you use have multiple elements or significant charactoristics, so that the filter which returns %11000000 filters light in two spectrum ranges, and another one which returned %11000001 would have added an additional range. This is purely speculative on my part.
A question. You say you basically have a wheel with 6 filter positions into which different filters may be placed. If you put filter "A" in position 1, does it return the same value as when you put filter "B" in position 1? If it is different, how do the properties of filter "A" and filter "B" differ? This could provide some insight into the significance of the bit patterns which are returned.
What I am getting at is that the returned value might be telling you not the position, 1-6, of the currently-used filter, but its physical characteristics, read somehow from the filter itself, e.g. UV filtering. Perhaps you could provide a description of the filters which you have.
