The funda for the auto numbering as follows
# In the Prefix box, enter up to 3 characters, symbols or numbers.
Prefixes are system-wide and are used for all system-generated numbers for the selected record type. If you change the prefix for a record type, it will not change the prefix of numbers that have already been assigned.
# In the Number box, enter the starting number.
If you have not set a numbering format before, the Number box displays 1000. After you set the numbering format and save your settings, this field is set to read-only and you cannot modify it.
# If you are setting auto-numbering formats on any tab except Articles, in the Suffix Length list, select a number
the max value will be 99999 as per the length specified,
but once it will reach 99999 and we will create the next record the value will become the next one 1000000 and it will keep going.