— 27% said they were likely or very likely to buy a wearable device
— 67% of those said they were likely or very likely to buy the Apple Watch

“Those numbers came up way higher than I was expecting,” says Tamara Gaffney, principal analyst, Adobe Digital Index.

If you do the math, 67% of 27% equals 18%, a ratio that Gaffney says is probably too high because of the way the questions were asked. Pressed for her own prediction, she estimates that over the next six to 18 months she could see 10% to 12% of Apple users buying the device.

“Ten percent. That’s my guess. I’m going to go a little low here.”

Apple as of last June had sold 800 million iOS devices. If 500 million are still in use, Gaffney’s 10% would represent 50 million Watches.

Surprised by the level of interest, Gaffney has been digging a little deeper. “What I’m discovering,” she says, “is that that now that people have a larger screen smartphone in their hands, there’s an increased benefit in having a really really small smartphone on the wrist.”

Follow Philip Elmer-DeWitt on Twitter at @philiped. Read his Apple (AAPL) coverage at fortune.com/ped or subscribe via his RSS feed.