318 Timing Chain Question.

For every one revolution of the crank the cam goes 1/2 turn. Turn the crank one revolution and the marks will be correct. If both valves are closed intake just closing that would be firing stroke . Install the distributor with rotor pointing to No.#1. No need the take the chain off. As long as the dots were 6 or 12 respectively you did nothing wrong except possibly distributor rotor location changing 180 degrees