If your sleeve cast-on is wider than you expected, there are two possible explanations!
First, full-length sleeves do give a few inches of ease in the wrist. This generally matches ready-to-wear clothing convention, and does not look roomy when worn. This tee shirt has 3'' (7.5 cm) of ease in the wrist:
However, if you'd like to adjust the wrist ease before generating your pattern, you can do so by clicking the "customize fit specifics" button at the bottom of your design's page.
Alternately, it's possible you chose a straight sleeve shape instead of a tapered sleeve shape. In CustomFit, a straight sleeve is a sleeve that contains no shaping. A tapered sleeve is slimmer at the wrist than the bicep. You can see which sleeve shape you've selected in the "Design Choices" part of your pattern information.
If you selected a straight sleeve and intended to choose a tapered sleeve, please get in touch with me!