The only ones you need are the display and edit patterns. I tried putting a pattern of zz9.99 into a numeric field object and got the correct format when I entered 123 into the field using Reader. It reformatted it into 123.00
When you dont see the pattern applied, it usually means that you have enter in data that has violated the pattern you have specified in Designer. So if you enter 1000 into this field, no pattern is applied since it is greater than 999.99 (the max).
Also, check the locale, the decimal digit might be messing up the pattern