Calculate the number 7490

Walking through Chinatown, a tourist is fascinated with all the Chinese restaurants, shops, signs and banners. He turns a corner and sees a building with the sign, "Hans Olaffsen's Laundry."

"Hans Olaffsen?", he muses. "How the heck does that fit in here?"

So he walks into the shop and sees an old Chinese gentleman behind the counter.

The tourist asks, "How did this place get a name like "Hans Olaffsen's Laundry?"

The old man answers, "Is name of owner."

The tourist asks, "Well, who and where is the owner?"

"Me, is right here," replies the old man.

"You? How did you ever get a name like Hans Olaffsen?"

"Is simple," says the old man. "Many, many year ago when come to this country, was stand in line at Documentation Center. Man in front was big blonde Swede. Lady look at him and go, "What your name?" He say, "Hans Olaffsen." Then she look at me and go, 'What your name?'"

"I say, Sem Ting."