Pressing People → Customer in a ticket, displays all that CustomerIDs tickets. However, since the May 31 update, it also displays Open tickets (customer) (20885) under Customer Information. Pressing that takes one to https://ticket.wikimedia.org/otrs/index.pl?Action=AgentTicketSearch;Subaction=Search;CustomerIDRaw=;StateType=Open
I'm assuming this is supposed to tell how many open tickets exists for that customer, but it is misattributing 'all' tickets to that customerID since there is no CustomerIDRaw. "20885" is most likely how many open tickets exists in the system in total, and not from a specific customer.