AutoGen will locate the last available number in any series. It does not fill in gaps as that would be problematic and slow down the procedure. If 10000 starts to appear, it means you have run out of numbers in that 5 digit sequence.
Example: 10000 means 99999 has already been used.
If you have hit the limit in 5 digit numbers you will need to change the AutoGen setting to 6 digits. If 6 digits are also in use in the 999900 range, you may need to assign 7 or even 8 digits.
To change the digit count in AutoGen for the A or C option, select Manager on your RMS server, Utilities, AutoGen, and change the sequential setting to next higher number. Click Generate, then Yes to make your change.