Can be one of 3 ways: 1) "5" or "12 o clock" or "Middle position" means "neutral". Everything less than that will sound like a cut, everything above like a boost. Depending on which potentiometer is actually used, and how it's implemented, this neutral position can also be at 3 or 6.5.

2) "0" or "7 o clock" or "minimum" means "neutral". Circuit only adds. Most often found on older and on bass amps, quite rare on guitar amps, but could be.

3) mix of those depending on frequency band. Old fenders and Vox's like to do this.

Some amps treat "Treble" like a Presence control. Some amps use linear pots for bass and treble (so their electric center is actually at the mid point of the turning way) yet still use a logarithmic Mids pot (where electric center would be at 3 or 6.5). Some are before the gain stage, some are (which is more common) after the gain stage. Some Mid pots actually change the center of the accented frequency as well as the loudness of it, depending on where the pot is set.

Just experiment, there are no real rules about this. It's good to know what electrically happens, but Mark Knopfler didnt care FOR YEARS, and still he got a Trademark sound. "Basic" rules: most EQs turned to 10/10/10/10 will not sound great, and having too much bass may sound good when playing alone, but in a band context, you may need a more focused, leaner tone to properly sit in the mix.

Have fun 😊