Can you take a screenshot of your gradebook and share? Make sure to cut out any names of students or other identifiers. Also including a picture of Categories and Items page would help.
Happy 
oodling!
Marty Soupcoff
Marty Soupcoff による投稿
I was able to make a category with more than 1000. Note: My category total is at top.
I don't know how you have categories or items named so I can't give an exact formula but maybe this forum post will push you on the right route. It was another user I was working with that was looking to do something similar. Their formula is near the bottom of their post and just in case I explained how it works in my response below that.
Happy oodling!
I don't think the 1.8 Moodle Docs available anymore (at least I can't find them) so I can't find out how the gradebook use to be set in that version. You could create a new category and put everything within it but not sure if that will change how it calculates. It is worth trying though.
It looks like the old Categories & Items page wasn't as helpful as in 1.9 or 2.x because it doesn't show the weights or aggregations selected.
I know I asked previously about getting access to your site and look at the course you were doing it in. As a slight modification, do you think you could get me access to a sandbox site in your Moodle instance? That way I can try and re-create the scenario in a 1.8 site but it won't affect any of the students as none of them will be enrolled in the course.
Happy oodling!