>>179-182

4-7-1
A team is not permitted to conserve time after the two-minute warning
of either half by committing any of these acts:

(d) throwing a backward pass out of bounds;

Penalty: For Illegally Conserving Time:
Loss of five yards unless a larger distance penalty is applicable.

When actions referred to above are committed by the offensive team
while time is in, officials will run off 10 seconds from the game clock
before permitting the ball to be put in play on the ready-for-play signal.
The game clock will start on the ready-for- play signal unless another rule
prescribes otherwise.

https://operations.nfl.com/the-rules/2019-nfl-rulebook/#article-1.-illegal-acts

5ヤード罰
10秒減
レディ・フォー・プレイで計時開始