72 360 first start question

#1 is confirming true TDC (that when the slit is on zero that the piston is actually at true piston/deck TDC). The slit was 10 deg off from actual/true TDC? #2 is confirming correct crank to cam phasing which includes lining up the dots which I'm sure they got right and that the cam has no error in how the lobes were ground on the stick at the cam factory (which is rare) and that the tchain/gears are marked correct (errors are seen somewhat regularly) and step 2 is confirmed to the nth degree by degreeing the cam & rockover gives us a reasonably close idea of where phasing is. With the slit on TDC on the tab either #1 or #6 cyl is on TDC compression. To tell which one you are on, if the rotor is on #1 then #1 is on compression (its firing so has to be on compression) and you go to its companion cyl which is #6 & check the rockers on it for rockover. vice versa. I'm still bothered by the slit being 10 deg off for #1 as that is somewhat rare but your procedure sounds OK unless we missed something