He was speaking about the whole gospel, when referring back to it. He is now moving forward from that reference to talk about the resurrection. vs 2 2By which also ye are saved, if ye keep in memory what I preached( past tense) unto you, unless ye have believed in vain.
Sir my only pointing out is that when paul preached to them in the past, he preached limited atonement as part of his gospel message. Thats all I am saying. I am quite aware of the overall context.