Min Xu wrote:
I wanna show there are 40 students got the grade between 70 and 90. I
want to have both 70 and 90 on my horizontal axis, and a bar
representing 40 students standing in between the numbers. How am I
able to do this? Thanks a lot.

One way would be to leave a blank category between 70 and 90, and place
the data next to it. Something like this:

No.Students
70
40
90

Now nothing will be plotted at the labels 70 or 90, but a bar
representing 40 students will appear between them.