Events in progress - Users logged in at anyone time - Query

Thank you v-qiuyu-msft, your example was of great help!

I had to do it slightly differently in the end to get my desired outcome but i do have one more question... 

I have now combined the tables to give me one record per event (user logged in and logged out). 

I have my number of users online at anyone time and i have Bins of time (1min,15mins,30mins ect) and that works well for graphs, apart from i would really like to also show the minimum for any given time range. For example if the 1min Bin is showing a period with 1 user logged in, even in the 30min bin i would like to overlay that minimum value over the calculated value for that time period. (14:03 is my example)

This is one of the measures i am now using to give me users logged in (i play with the min/max and >< as it shows me a slightly different picture) Found from here classifying-and-solving-events...

S1 = Calculate (
CountRows ( events),
Filter (Values ( events[LoginDateTime] ), events[LoginDateTime] <= Min ( DateTime[DateTime] ) ),
Filter (Values ( events[LogoutDateTime] ), events[LogoutDateTime] >= Min ( DateTime[DateTime] ) )
)

and i get this for example...

And for the 30mins...

But i would like to plot the min for each 30min period, for example  14:00-14:30 would be 1...

Can you help again or can anyone else? 

Thank You