Kris, you've got to figure out how much ZDDP
by weight is in each amount of booster base oil vs the weight of the oil itself
(yup, the base oil weight that you also have to know by weight).
Then do the same exact thing for the amount of Rotella oil you are using. Nothing is done by volume, it is all done by weight.
Then you total the two ZDDP weights. then divide that number by the weights of the two base oils totaled together, then multiply that resulting very small fractional number by 1,000,000 to get your ZDDP PPM number for that mixture.
It isn't that easy to do. And you begin to get a feel why Boule said to do your mixing to the full virgin gallon jug, as he had to have something to hold still for his figuring which was done on a complex formula spreadsheet.
Boule did the spreadsheet and the table correctly, we all reality checked at the time using our various methods. The table was in line with the factory recommendations from Redline and Eastwood, differing only in that it starts up high because our Rotella base oils were already up high in ZDDP already.
Gotta watch that Redline factory recommended mix ratio stuff that is on the bottle and on their web page, it assumes you are starting out using Walmart normal very very very wimpy car oils.
(and some of you are ....... Castrol GTX indeed)