I haven't had the xB long enough to have the light blink for me, but...
I owned a 08 Toyota Prius and I was told it will come on every 5k miles to remind you to get your vehicle serviced. The light drove me nuts on the prius so I would get it serviced as soon as I could so I wouldn't have to look at the light. I read somewhere that there is a way to get the light to go out in the manual for the xB.
Megan

yep it comes on just before you hit 5k for your oil change. They will reset it at the dealer when you get your oil changed.

Yep...
It's in your owner's manual

first, push your odometer knob until it is at the odometer "over all" miles. turn your ignition to the off potision. then, with one hand, push and hold the odometer knob and with the other hand turn the ignition back to the on potision and hold it until you see it go "00000000" and then let go. you'll notice it will go "-------" then to " -" which it will blink a few times before going to "00000000", once it has done this, it is fully reset and ready to go.