Calculate the number 6159

A wealthy man was having an affair with an Italian woman for several months. One night, during one of their rendezvous, she confided in him that she was pregnant. Not wanting to ruin his reputation or his marriage, he paid her a large sum of money if she would go to Italy to secretly have the child. If she stayed in Italy to raise the child, he would also provide child support until the child turned 18. She agreed, but asked how he would know when the baby was born. To keep it discreet, he told her simply to mail him a post card, and write "Spaghetti" on the back. He would then arrange for child support payments to begin.
One day, about 9 months later, he came home to his confused wife. "Honey," she said, "you received a very strange post card today."
"Oh, just give it to me and I'll explain it" he said.
The wife obeyed, and watched as her husband read the card, turned white, and fainted.
On the card was written: "Spaghetti, Spaghetti, Spaghetti. Two with meatballs, one without."