What does it mean in a dimensional drawing when the diameter of a part to be made with A/3 for a diameter for a cylinder ?

What does it mean in a dimensional drawing when the diameter of a part to be made with A/3 for a diameter for a cylinder ?

See page two at bottom and I think the dimension is a linear equation. Find X = A/3 and Y = B/3 +10MM. I did the math and the two cylinder parts I made are not to touch corners. Just want to make sure cylinder diameters are correct. A is 71mm diameter and Y is 76.67mm diameter. So, to correct the touching cylinder corners and space apart according to drawing. Thanks.

A is a variable (or name given to other dimension) and there should be a value defined for variable A. So the diameter is 1/3 of that value.