For those using the AEMtuner software (Version 2 ems) here is a step by step of how to sync the Ignition timing.
Syncing the ignition timing when using and AEM is a key step in the start up process. Using a timing light to check physical timing at the engine matches the timing value displayed in the AEM tuner software will ensure the timing #s in the map and in the data logs are 100% accurate.
More ignition tuning info on the blog
Ignition set up and tuning AEMtuner