A 0.3 mm tab is probably too small for whatever material you’re cutting, because the cuts on either side produce a kerf that will just about meet in the middle. The as-cut tab length depends on the material; a good tab in 3 mm plywood will vanish in chipboard.
Running the laser power at 100% means the kerf is probably larger than you think, so it’s worth measuring:
I use 0.7 mm for plain paper, 0.75 mm for chipboard, 0.5 mm for adhesive sheet, 1 mm for heavy fabric, and so forth and so on. I use tabs at least four times the kerf in the material I’m cutting, although I tend to round upward.