Help deciphering bearing grinding marks

I have disassembled my 1500 T1 motor and it has the following inscription painted on the motor. I know it most probably is the undersize oversize markings, but is there a specific code that would have been used? The motor I believe was originally fully refurbished by Volkswagen King in Sydney.

20-22
30-30
and what looks like 5 plus minus 6 - the 6 is not fully legible so I am guessing and the plus minus is the plus and minus on top of each other.

I know I need to micrometer up the bearings, but was interested in what these markings meant.

Any ideas?
Thanks viiking

looks like imperial thousandsth. 20thou is just over 0.5mm and 30 thou is close to 0.75mm 🙂

or is it deck height's????.....more info req'd, maybe take a pick so we can see where it's written as that can shed some light.... too many numbers to be bearing related IMO