The constituent only has 8 payments remaining because your org doesn't have the site setup to increment the failed payments (add them on at the end of the pledge). This option is listed under the SDP (Site Data Parameter) DON_RECURRING_PLEDGE_FAILURE_INCR_DURATION, which you have set as blank so it defaults to FALSE:

"(Default FALSE) This SDP determines how failures to recurring payments are handled. When set to FALSE (default), failures to the recurring payment will NOT increment the duration. This means that if the pledge has a duration of 12, if there are 6 successful and 6 failed payments, the pledge would be marked as completed. If this is set to TRUE, then when a failure occurs, it increments the duration so that one extra payment can be obtained from the donor. This SDP has no effect if the pledge has no duration. If you set this to TRUE, please look at DON_RECURRING_PLEDGE_MAX_FAILURES to limit the number of extra payments that are tried for this pledge".

If you would like this changed to TRUE, please contact Support who will make the change for you.