In the edit percussion kit I have the toms listed low to high, but in the score the order is reversed. And why is tom 4 not named as such?
For some reason, there’s two separate collections, both Toms and Tom-toms in the instrument list. They will only get automatic numbering if they’re all from the same set, which the fourth one here is not.
The automatic numbering reflects the order in which you added the instruments, not their pitch order. Dorico considers all Toms (and all Tom-toms, for that matter) to be identical even though there are multiple entries in the list.
There is another option, however, bypassing all numbering issues: select all four entries in the Edit Percussion Kit dialog, then hit the Group: + button. You can then rename the entire “staff” into 4 Toms and be done with it 
Thanks for the reply hrnbouma, will give that a try. I had thought I had added tom toms from unpitched percussion and there were 5 of them of which I deleted one to leave 4 so I’m not sure what happened. Am I the only one who thinks this is more difficult than it needs to be?