The number displayed on the tab is stored on the city - it does not do that count in the database to display that number. Each time data is added/removed, it updates that count.
All of the streets in Vila Boa do Bispo have a creation date of the 28th, so I’m also unsure of why that value was 1. My guess is that there was 1 street, but the update removed that & added the 76 new streets.
If you happened to view the city at that moment in the process - it had removed the street (resetting the count to 0), and it had added some/all new streets but had not yet updated that stored count - then you’d see that 0 even though there were e.g. 76.
The “? miles” is due to that feature being added later than when the city was added. Any city without runners very likely displays the same “? miles” because the data has never been calculated.
Overall, any city without anyone who has completed a street in it are old/stale/likely-wrong. After someone completes a street, it’s put into the sync queue & since it has never been synced before it is first in line. That sync fixes up the city, but in your case it was so drastically wrong to begin with that it also marked you as finishing it.
Another aspect here is that the city sync infrastructure is continually (minutely) trying to run more city syncs. So, you saved your activity which set the completed street and a minute or so later queued the sync which corrected things and invalidated your completion.
