The previews may not be pixel-perfect! Official animal numbers will be supplied by the ministry during the tag manufacturing process - the official animal numbers shown on tag previews always start at 00001 and are intended to give an indication of the format of the tag, they are not the actual numbers that will be printed on your tags.
For incrementing Management Numbers, the numbers shown on the tag preview are the actual numbers that will be printed on your tags. The first and last tags in the run are shown so you can clearly see what the number range is.
If you would like leading zeros in your management numbers please type them into the start number box e.g. type 00001 to make sure all numbers are 5 digits long.