When KJ26 says forward he means it is leading the RF. If it is pushing/sliding the rf or tight on entry, move the RF lower portion back and use the 2nd mark on the frame to set it. I'm gonna say 6 and 8, based on the info below, i'm not 100% if thats true to your frame it was generic ultramax article i found
Step 3 – Setting your Caster
Each chassis comes with the right front caster set at 10° and the left front caster set at 8°. These settings are obtained when both sides have the center notches lined up on the caster blocks as shown with the left front in the center picture below. For almost all conditions, these caster settings will be a good starting point. However, there are certain situations where a different setting may be desired for a better weight jacking effect. For this case, both the right front and left front caster blocks come equipped with three lines both forward and backward from the original notch. Each line forward or backward is a 2° change in caster. Therefore, on the right front you can go as low as 4° of caster or as high as 16° of caster. Similarly, on the left front you can go as low as 2° of caster or as high as 14° of caster. The following figures illustrate how this works using the left front as an example with the picture on the left set at 6°, the middle at 8° and the right at 10°.
Caster is built into a racing chassis to promote weight transfer, which is a major factor in producing the bite necessary to negotiate each corner on the track. Generally, more caster will produce more weight transfer and more bite and less caster will produce less weight transfer and less bite.
So, on high speed, hard biting racetracks, less caster will be needed since the racetrack itself will be producing most of the necessary bite. Similarly, on low speed, low biting racetracks, more caster will be needed in order to produce the necessary amount of bite in the chassis.