Chemistry has math.

I'm not as well-versed in this as EP....but....I believe that we are using something known as Charles's Law that says :

V₁ T₂  = V₂ T₁        so

620 * 325 = V₂ * 293      divide both sides by   293

(620 * 325) / 293 = V₂   ≈ 687.7 ml