The door is probably touching the side jamb at the top of the door leaving no gap at all.
Gap under wooden front door.
That is a lot of room for unlevel you have there.
Make marks through the pre drilled attachment holes onto the door proper.
The odds are you ll see a larger gap at the top of the door on the top edge that s above the handle or door knob.
Reset the door so that it is level and plumb.
Position the gasket so it sits against the door tightly on the inside when the door is closed.
I have never seen a door set with that big of a gap unless it was to get past floors that were not level.
Place the sweep at the bottom of the door and align the sweep edge so that it blocks the door gap.
Remove the adhesive backing and stick.
Shim it and nail it and hang the trim.
Install a foam weatherstripping gasket around the door frame.
The standard i use is 1 2 over finish floors 3 4 is acceptable.
New upgrade huge gap door draft stopper 3 2 5 w widened door sweep seal gap up to 1 4 5 for interior exterior doors keeping draft noise dust and unwanted animals out 3 2 5 w x 39 l white 4 6 out of 5 stars 1 076.
If you have a large gap at the bottom of your door that may be helping the door to stay plumb.
If you ve noticed a large or small gap on the bottom.
Pilot hole the marks.
To fix the issue the doors need to be removed bottom of the jambs cut and reset the door.