Count of remaining seats in a Room.

Hello, I’m trying to make a column which counts the number of remaining seats. I have two different tables.

Table 1- Implementing the new HR operation Model in Asia: The table which contains all the data about the events and the initial seats (photo 1)

Table 2 - Responses 2018: the table with the registered users. In this table I have a virtual column which counts the remaining seats of each event. (Photo 2 and Photo 3)

The remaining seats should be 17, because the initial seats was 20 and we have 3 registered users. But it’s 19…

I’m pretty sure that the problem is the formula of the remaining seats:

=[Initial Seats]-COUNT(Select(Responses 2018[SessionName],[SessionName]=[_THISROW].[Session], [Time]=[_THISROW].[Time]))

Can anybody help me?

Thanks.