I'm far from an expert but it may have been counting all the characters you use in coding your signature to be in colour, different sizes etc which, looking at your signature, may be over 2000 characters in total.
I didn't count so don't blame me if I got it wrong.
Erm.. Yours is like 5cm, and pretty full - no problems for my eyes.
You are right about that, I guess it was just the terminology you used that prompted that response. When you said "as much as we like within those 10 cm" I imagined sigs crammed full with as many symbols and effects that can be used. It might be my overimaginative mind though.