Assuming I'm not missing anything from the game log, the ball was run on second down six out of 15 times during this game. If you ignore the fourth quarter, the ball was run on second down six of 12 times this game.
2nd & 3 at SEA 32(13:30 - 1st) K.Walker right end to SEA 35 for 3 yards (F.Warner).
2nd & 10 at SEA 35(12:40 - 1st) (Shotgun) D.Lock pass short right to D.Metcalf to SF 44 for 21 yards (J.Brown; C.Ward).
2nd & 6 at SF 40(11:00 - 1st) (Shotgun) K.Walker up the middle to SF 40 for no gain (N.Bosa, D.Greenlaw).
2nd & 7 at SEA 32(7:22 - 1st) K.Walker up the middle to SEA 32 for no gain (K.Givens).
2nd & 14 at SF 18(2:00 - 1st) (Shotgun) D.Lock pass incomplete short right to K.Walker.
2nd & 8 at SEA 39(13:36 - 2nd) (Shotgun) D.Lock pass short left to W.Dissly to SEA 42 for 3 yards (D.Lenoir, D.Greenlaw).
2nd & 6 at SF 49(12:07 - 2nd) Z.Charbonnet right tackle to SEA 48 for -3 yards (J.Kinlaw).
2nd & 7 at SEA 48(7:01 - 2nd) D.Lock pass short right to K.Walker to SEA 49 for 1 yard (F.Warner).
2nd & 13 at SEA 5(0:25 - 2nd) (Shotgun) Z.Charbonnet up the middle to SEA 7 for 2 yards (N.Bosa).
2nd & 10 at SEA 31(14:51 - 3rd) (Shotgun) D.Lock pass incomplete short right to N.Fant (D.Lenoir).
2nd & 8 at SEA 15(9:24 - 3rd) (Shotgun) D.Lock sacked at SEA 15 for 0 yards (C.Ferrell).
2nd & 9 at SEA 32(7:31 - 3rd) (Shotgun) Z.Charbonnet right tackle to SEA 28 for -4 yards (C.Ferrell).
2nd & 6 at SEA 39(11:52 - 4th) (No Huddle, Shotgun) D.Lock pass incomplete short left to D.Metcalf.
2nd & 2 at SF 48(6:39 - 4th) (No Huddle, Shotgun) D.Lock sacked at SEA 44 for -8 yards (R.Gregory).
2nd & 9 at SF 44(4:54 - 4th) (No Huddle, Shotgun) D.Lock pass short middle to K.Walker to SF 41 for 3 yards (I.Oliver).