Query on Check Digit used in Next Numbering for Account ID (AID)

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We have defined Next Numbering for Next Account ID (AID) with Check Digit ticked.

Now AID is 8 character. With check digit enabled, the last digit is a random number and is automatically generated.

Since AID is 8 character, the maximum number of AIDs that we can use is 99,999,999. My question is that if we enable check digit, do we still have 99,999,999 numbers of AID, or since the last digit is a random number the maximum number of AIDs that we can have is 9,999,999.

Please find below a live example:

In F0901, last AID used is 21673061. However the count of F0901 is 2134005.