Can anyone out there help me with a problem I’m having?

I have a database with 10117 records in it. Each record is numbered from 0001NHP to 10117NHP. Sometimes I have the database in alphabetical order of names and sometimes in number order. The problem is when I put it into number order. It runs in order until it gets to 0999NHP then it jumps to 10000NHP runs to 10009NHP then back down to 1000NHP then to 10010NHP which runs to 10019NHP...