Then you need to ignore those people. If they can't do simple math, I wouldn't take any recommendations from them, either.
To figure an engine's displacement, the formula is:
pi / 4 x bore squared x stroke x # of cylinders
Now, pi (3.1415927) divided by 4 equals .7853982, so the first part of the formula will always be .7853982:
.7853982 x bore squared x stroke x # of cylinders
Now, a 302 has a 4" bore, a 3" stroke, and 8 cylinders, so, by substituting those numbers, you get:
.7853982 x 4 squared (16) x 3 x 8 or:
.7853982 x 16 x 3 x 8 = 301.5929 cubic inches
With me so far?
Okay, now let's say you bore the engine .030" over, which means increasing the bore diameter of each cylinder to 4.030". Then the formula would look like this:
.7853982 x 16.2409 x 3 x 8 = 306.13375 cubic inches.
If you were to bore it .040" over, the formula would become:
.7853982 x 16.3216 x 3 x 8 = 307.65492 cubic inches
Get it?
As far as your oil problem goes, if the engine has been ran, then clean the dipstick and check it again. When you see where the oil mark is, get a punch and a hammer, and punch a dimple at the top of the oil line. This is now your new, accurate dipstick.
Take care,
-Chris