It depends if the website maintaining the numbering is counting DS/DSi enhanced/DSi Exclusive in the same dat, or separate (so 3 possible numbering).
GBAtemp is numbering both DSi separately from DS releases.
Advanscene (offlinelist) is numbering them all in the same list.
There's no rules on the number, it's a method created by rom providers websites, not by the ROM dumper release teams, so games don't have official number to recognize them.
Some websites are also counting hardware dump (action replay, flashcard dump, etc.), so there's even more different possible number.