Mom buys lottery tickets every week,

For several years now, she always stubbornly sticks to the same fixed numbers.
Then, every time she argues with Dad,
Mom always has that classic line.
“If I really win the first prize in the lottery, just watch me!
As soon as that money is in hand, I'll immediately stamp the divorce papers,
Each goes their separate way!”
But Dad, every time he hears this, doesn't even grunt,
He just brushes it off with a hearty laugh.
I was puzzled, why is he so calm...
Today, Mom was grumbling in the distance,
Dad secretly showed me the lottery numbers,
They were actually the same numbers, hahaha
And Dad buys two tickets every time.