99' GC timing chain installation help

I have a 99' Grand cherokee 4.0 liter laredo. My motor had what I would call a "catastrophic" failure at 193K. I have since removed the motor, had a machine shop go through everything and now I am in the process of getting everything back together. My problem is this....My manual claims that when I install the timing chain, Assuming that the two timing marks on the gears are aligned so that a straight edge would connect both timing marks as well as go straight through the center of both centers of each gear. Second, to double check the alignment of said gears there should be 15 chain "pins" between both timing marks. Unless I am missing something very important this is impossible. I keep coming up with 20 pins everytime. I even bench made up the old assembly and still come up with the same 20 pins. If I use the 15 pin method, the timing marks never line up in any significant order ie, TDC @ #1 cylinder. I could really use some help here. I would also assume the the timing marks are still the single dimple toward the outer edge of the gears. I by no means am a newbie to the world of engines, but this one has me stumped. Also, The book tells me to reinstall the thrust pin and spring back in to the camshaft gear prior to reinstalling the bolt. During the teardown, There was only a bolt and no thrust pin or spring. Any suggestions. I do not wish to proceed with the build until I get some input on the timing.
Thanks for the help.