Is there a mathematical difference between 0.3 and 0.30?
Yes.
0.3 may be exactly 0.3000000 (etc), it may not.
0.30 shows that there are *no* smaller numbers follwing the
terminal zero, so 0.30 *is* 0.3 *exactly*.
Tip: *do not* just add a terminal zero if you cannot jusify the
precision. A measurment of 0.30 inches ( or cm, mm, whatever)
implies a measurment that is *totally* accurate, down to the
wavelength of light and beyond!