Why did this character come back to life in Cemetery Man?

In Cemetery Man (1994) it is explained that some people buried in the cemetery come back to life after 7 days for an unknown reason. Francesco, the keeper of the cemetery, is in charge of killing them if they do.

Early in the film, he meets a woman who has buried her husband and in their first conversation he asks her how long he's been dead and she replies its been two weeks. Francesco says "good" as he is relieved that the husband will not come back since its been more than seven days. Later on, however, when he and the woman are making love on the husband's grave, he comes back to life and bites the woman.

So why/how did he come back to life if it had been more than seven days?