What’s the difference between K1 elongated and K1 elongated twice?

A K1 elongated stitch should have the yarn wrapped twice. A K1 elongated twice would have the yarn wrapped three times, a K1 elongated thrice would have four wraps, and so on. 

You can check the full description of how to work a stitch by viewing the stitch library (via Preferences, which is found under the Stitchmastery menu on macOS, and under Tools in Windows) and opening the stitch in question. You can find out more about this here: Viewing and creating User Stitch Libraries.