Welcome to the forum!
Short rows are extra rows knit into a project in order to shape it. You’ll be working partway along the row and then turning as you would at the end of a row and then working back over those same sts. There’s a video at the top of the page if you need it.
For your pattern it sounds like you work to 4sts from the end, turn and work back. On the next row work to 8sts before the end and turn. Keep working 4 fewer sts every other row.
In order to avoid holes, you usually do a wrap and turn as in the video here or some other method like German short rows, shadow short rows etc.
Can you give us a pattern name or a link to the pattern?
Very pretty pattern. I love the detail on the back.
The stitch number should stay the same. Picking up wraps foe example, and working them together with a stitch maintains the original stitch number. That’s true for other short row techniques that I’ve seen.