Good afternoon,
I'm assuming you have some type of Lycoming engine with Slicks Mags? If that's the case your number 1 cylinder is the forward cylinder on the right side. Depending on what type of TDC locator you are using find 25 degrees or what ever is on your engine data plate or engine TCDS. Slick mags install with a timing pin located in the housing with the ignition wire cap removed. install that locator pin in either the "L"/"R" (mag rotation) . Install the mags, remove the locator pin and then fine tune them to the number 1 cylinder with whatever type of "buzz box" you have. If they'll time in that position the rest will be fine. If they won't time in that position you probably have some type of E gap setting problem which is highly unlikely since you just had them inspected. Contact me if you'd like.
SteveL
AP/IA