How to write query to see the change in the number of errors in the 1 hour interval?

As I mention on the title, I want to find the difference of error counts in 1 hour interval. When I use delta() or increase() function, the results are duplicated. I guess I have to combine functions. However I couldn’t achieve that.

The example scenario:

Number Of Errors at 13.00.00 = 100 Number Of Errors at 14.00.00 = 120

So the result is +20