This first photo is showing a hem pressed. If you try to sew over this area where the serged seams are stacked up with a cover stitch machine, at the very least you will get a pile up of smaller stitches as the feed dogs struggle to push over the extra bulk. More likely you will get skipped stitches. So, open up that nicely pressed hem:
And see where the fold is pressed into the seam allowance. Here is where you will clip to, but not through the furthest needle thread in the serged seam:
And flip the seam allowance in the hem the opposite direction from the seam allowance in the body of the garment:
Now you can fold the hem back into place along the pressed line and the seam allowances will nest and be much flatter:
Be sure to put a pin here to hold everything in this orientation before you begin sewing the hem. I have been doing this for years and have never had a seam pull out in the hem area as a result of that clip. Please ignore the bad manicure, or actually, the complete lack of manicure, and ragged cuticles. I went straight back to the lotion after every hand-washing and cuticle cream at night regimen as soon as I saw this photo.