NCAA - Clock Status

[FBullock]

NCAA RULES ONLY (Doesn't apply to NFHS)
A's ball, 4th and 3 on B's 7 going in. A 32, the runner, fumbles the ball at the 2 yd line and it rolls into the EZ where it is recovered by end, A 88.
Under the 4th down fumble rule, it is A's ball, first and goal at the spot of the fumble, B's 2 yd line.

When does the clock start and your rule support for your answer??