The lace or skin on a front hairline is cut in a saw-tooth shape—Zigzags.
That is called the scalloped front.
It broke up the straight front hairline and made it slightly more realistic, creating a softer and more natural appearance.
We usually don't make scallop to lace material. Lace can easily create a very natural hairline; meanwhile, lace scallop will make the lace edge fray more rapidly. The scalloped front usually applies to skin material only.
Here below is the scallop size options for your reference, you can compare the scale under the sketches and order a proper scallop size for yourself.