How did the second wish come true in the monkey paw??

Mr. White's first wish using the cursed monkey's paw is for two hundred pounds. Unfortunately, the White family is horrified to learn that their son, Herbert, has died in a machine accident at work and the company has given the family two hundred pounds to pay for their son's services. In part 3, Mrs. White remembers that her husband wished for two hundred pounds using the monkey's paw and decides to ask for a second wish. Despite the fact that her son has been dead for ten days and is buried, she takes the monkey's paw and wishes for her son to be alive again. After the talisman initially falls to the floor, the home becomes completely silent, and the couple heads back to bed. While the couple is lying in bed, Mr. White suddenly hears something knocking at his door. His wife realizes that her second wish has come true and that Herbert is the person knocking on their door. Fortunately, Mr. White manages to make a third wish before his wife opens the door to see her decaying zombie son.

After Herbert's death in a grisly work related accident, Mr. and Mrs. White slip into depression. Herbert's death seems to prove the powers of the monkey's paw because the Whites receive, from Herbert's employer, precisely the same amount of money which Mr. White had wished for.
Finally, a week after they buried Herbert, Mrs. White can take the melancholy no longer and she seeks out the paw after realizing there are still wishes to be made. She tells Mr. White, "We've only had one...we'll have one more. Go down and get it quickly, and wish our boy alive again." Despite his fears and best judgement, Mr. White, at the behest of his now fanatical wife, wishes for his son to be "alive again."
As with the first wish which cost Herbert his life, the second wish has even more ghastly consequences as Herbert's mutilated corpse lurches back to Laburnum Villa from the cemetery two miles away. What Mr. White had feared comes true as Herbert's corpse pounds on the door to be let in. Only the last wish spares the Whites from seeing the hideous creature that was once their son.