Typical error when the midi is exported from FL studio using the Midi Out Channel method. In UTAU, you'll need to click the yellow box to set the correct tempo. You should also go to Bar/Measure 0 and right click on the 50000 (or whatever it says) and delete that.
To prevent this error happening again, you can export midi in FL studio directly from the piano roll by clicking the [V] arrow in the top left, then going File and Export Midi. Alternatively, don't use FL studio if you find tempo or time signature important, because it handles those things poorly compared to other DAWs.