Move all your saves to a usb drive. Start a new game which should reset the counter. [Make sure the auto saves are gone first]. Go back to dashboard after you make a safe game. [Not sure if autosave will work]. Copy 1, one, save game back to the hard drive. [The one you want to reset].
Load your high numbered save game. Delete it. [That's why it needs to be a COPY]!
Go to Whiterun, go to 3rd person view, save your game.
At this point, the only saves on your hard drive should be the new game save #1 & the high numbered Whiterun save. Delete any auto saves. Go back to dashboard. Restart the xbox.
[May need to repeat this next part].
Start the game back up, load the Whiterun save. Delete the save. Go in & out of a building several times to get autosaves stacked. [I recommend the tavern].
Exit the building, delete all the autosaves.
Now the only save you have is the new game save #1
Go into 3rd person view, while in Whiterun & not in a building. Save your game.
IT SHOULD BE EITHER SAVE #1 OR #2.
IF IT DIDN'T WORK. GO BACK TO DASHBOARD, RESTART GAME AT THAT SAVE. REPEAT THE WHITERUN TAVERN AUTOSAVE PORTION, DELETE ALL SAVES AGAIN. [EXCEPT FOR SAVE #1].
Try to save the game again.
If it still doesn't work. Try moving the save #1 to a USB drive & then back to the hard drive. & try the autosave portion once again.
It has worked for me for FOUR different characters. All for saves are less than safe #4.
[I also messed with the date stamp on my xbox a few times. I don't think that affected the saves at all].
Since there is no true way to reset the counter, it's very frustrating to get it to reset.