Put the tentioner in and roll the motor by hand a couple revolution back to TDC and look again. That is as good a reading as you will get without a dial indicator. DO NOT leave it advanced.
The natural place is for the right cam to be slightly retarded as there is way more chain between it and the crank. Even with a new chain the wear of the gears causes the same action (right cam retarded).
The marks you are using are good enough to pick the right chain position. They ARE NOT accurate enough to judge the degree of retard or advance. This must be done with a dial indicator. Years ago I used to dial indicate them and correct to within two degrees with offset keys. On an old chain with 14 degrees of retard this would really bring back some power.
It has been years since I quit doing this. We now roll through a new chain if it had that amount of retard and accept 5-6 degrees that they always seem to show (on the right cam).
Bosch Master, ASE Master, L1
33 years MB technician