How do you remove the old threshold?

I have the instructions and am about to install mine however my question is how do the adjusting screws work? Since no part of the adjustment hardware is attached to the adjustable riser how does it work?
To answer your question after cutting the threshold to fit Remove the top riser Drill three evenly spaced holes in the (wood) base (under the riser) and secure threshold to subfloor.
Word for word instructions:
1. Measure width of door and saw threshold to size.
2. Remove top riser and insert T-Nuts into wood base holes by tapping with a hammer or mallet.
3. Drill three evenly spaced holes in base and secure threshold to subfloor. (Fasteners not included)
4. Insert screws into riser. Apply washers with raised flare away from riser.
5. Place top riser on wood base and tighten screws to desired height.

For the person who posted about changing the color of the wood threshold. Why not just sand the wood portion and restain it the color you want? Much cheeper than replacing the threshold.

F