You can get the value using length(); I got the number of files tagged #Ticket like so:
TABLE length(rows) as ticketCount
FROM #Ticket
GROUP BY true
It was a little tricky to figure out the summing, but I got that as well. Here’s what I use to see how many points I’ve accumulated in my #Tickets for the current Sprint, as well as how many more I need to hit my current goal of 10:
TABLE sum(rows.Points) as TotalEarnedPoints, 10-sum(rows.Points) as PointsToGo
FROM #Ticket and [[Sprint Ending 2021-04-08]]
WHERE Ended != null
GROUP BY Sprint