I slowed the video down to .25 speed, and it looks like a regular zig zag stitch, for the initial hem seam; Then a straight stitch to 'flatten the seam allowance formed by the first seam .
well this is how you ACTUALLY crop a tee. instead of being a tik tok genius and just using scissors to cut it, then you have a tacky cropped tee that rolls up at the bottom
If you’re barely starting out, & this is difficult, here’s a idea that maybe is a little easier? I’ve seen it on other channels. Put the shirt on inside out. Don’t cut off the original hem. Use this to avoid having to re-hem once you shorten it. Determine how much you want to shorten it. Iron up the hem. Sew a straight stitch right @ the end of the original hem. Cut off excess material. Press hem downwards away from the top. On the outside of the top, stitch close to the seam all around. (Edgestitch) Done. I know I’m sorry, there’s so many steps. This is actually the method I use for hemming everything, in order to keep the original hem.