On fields I have Type set to Number in FileMaker Go, the keyboard pops up as numbers.
Are you sure the number field is set to number and not text? (Manage Database>Fields. Go to field and look at Type.
I would like it to show up only the numbers with big buttons. I know that there are such a state in the iOS, because there are some apps that call this keyboard when you are going to enter only numbers.
I would like it to show this keyboard: