The second marking won’t be swing weight. Changing the length of the club changes the swing weight. Add weight to a shorter club and lower weight for a longer club. Titleist has a standard swing weight unless otherwise specified at the time of ordering to a different swing weight.
Weights are available to order through your authorized dealer. If you select the Clubs tab on this website, pick a club, then scroll down until you find a button for Custom (Catalog). you can open the online brochure to page 26 (Weight options).

Thank You,

I am a tinker.

I had used the weights in the 915 series to dial in shaft flex/clubhead delivery.

The full weight kits are generally limited to local shops, although they can be ordered through local shops. Most specify a swing weight at the time of ordering and rarely change. There are also non-OEM options on the web. They can nullify the 1 year guarantee and some may cause damage. Checking the catalog, one set of weights won’t fit all drivers or fairways. Just check carefully.