Here we go, well you did ask. Grab a

No i don't use calipers, i did try but i could never get used to it even though i used them daily when i was a CNC machinist.
I use a x8 magnifying glass and plus 3 reading glasses to see the markings, i couldn't do it otherwise without them.
What i do is i use different parts of the plunger to get the dose i need.
If you look at the image below, number 1 is the top of the plunger, 2 is the bottom part of the top, then there is a gap in the plunger to number 3 then number 4 is the bottom part of number 3, so in affect 3 and 4 are the same as 1 and 2.
Are you following this lol.
What i do then to get an accurate dose is say i want 1.125u i will draw about 2 units out (knock any bubbles up) and use position number 2 on the syringe and take that to 1.5u line and that takes the top (number 1) to the 1.125u position.
If i need 1.25u i will use number 3 and take that to the 2u line and that takes the top (number 1) to the 1.25 position.
I works well for me with accurate dosing but sometimes it can be very very slightly out as in i might think it's slightly too much or too little so what i do then is use the thickness of the line/marking to make an even finer adjustment, either top, bottom or middle of the line/marking.
When i have finished giving Duke his dose i always put the syringe back to how it was before i gave him his injection then i can use that as a marker for his next dose.
It does sounds complicated but it's very easy to do once you get into it, but you do need a good magnifying glass.
This method will not work on u100 as i have tried it, they are completely different.
Also make sure the plunger lines up on the zero line before starting as some Prozinc syringes can be out by upto 1/4 of a unit, i now use sol-vet u40 syringes and they seem a lot better for lining up.
This is 1.125u with position number 2 lined up on top of the 1.5u line
This is 1.25u with position number 3 lined up with the 2u line.
The photo below is set to a 1.75u skinny, as you can see the plunger position number 3 (see diagram above) lines up on top of the 2.5u line.
View attachment 64691
The photo below is set to a 1.75u fat, as you can see the plunger position number 3 (see diagram above) lines up on the bottom of the 2.5u line.
View attachment 64692