If I understand this correctly, you mean that, hypothetically, a spammer would post the required amount of posts to warrant a mute (say, 7), then they would get a warning, then they would have to post 7 more things to be muted.
Assuming I got that correctly, perhaps a better alternative would be to get a warning after a smaller number of posts (say, 5 or 6), then get a mute when they reach 7 without resetting the number (i.e. after 7 total posts, so the total number of possible posts without mute doesn't change).