How do I add 1 to every cell from B10 to B16?

All cells from B10 to B16 contain constants. I want every one of these constants to be incremented by 1.

I tried the following: Select B10 => put the cursor over the small square at the bottom right hand side of the cell => hold down Ctrl => a + sign comes up => hold Ctrl and drag down to B16.
If I release Ctrl before releasing the left mouse click, the entire selection gets autofilled with the first constant.
If I release Ctrl after releasing the left mouse click, the entire selection gets autofilled with numbers obeying a rule that I have not figured out yet, but it is definitely not increment..