Are you sure that you didn't rename the custom field? Also, does it appear incorrectly on one machine, or multiples? It's possible that the form could be cached incorrectly.
Try removing the number field from the CI form and saving and closing it. Then check your custom field and verify that it is named correctly and doesn't have a duplicate name shared by another field. Re-open your form and add your custom field back. Then close down the client entirely and log back in to check if the form updated. You have to close all the way out because the forms are cached when you first launch the client.
If that doesn't solve your issue, try clearing the client's cache ("Tools"->"Options"->"Advanced" tab) and see if that helps.
If that still doesn't clear it up, check the "%SD_CLIENTHOME%/data" folder for a "Forms.dat" file. Move the file out of the directory or rename it to back it up. Then launch the client and see if the form is updated. The forms.dat will be re-created.