There is no 'magic' number for any of the syringes. Decide what YOUR one unit measurement will be then figure from there. Divide by 4 to get your quarter unit measurements. I'll share what I use for the BD's - doesn't mean you have to use it too:
.25 - 33
.50 - 65
.75 - 98
1.0 - 1.3
1.25 - 1.63
1.50 - 1.95
1.75 - 2.28
2.0 - 2.60
HUGS!!!