SRAM dub crank chainline Any SRAM experts out there? Zero experience with SRAM dub. Used Hollowtech for years before... Ordered SRAM GX dub crankset. Advertised specifically for 49mm chainline. Arrived pre-assembled with a chainring that is direct mount 3mm offset... From limited information online it appears that 49mm chainline is achieved with 6mm offset and 3mm chainring will result in 52mm chainline respectively (BOOST). Am I wrong here or did the bike shope send the wrong chainring? Any advice appreciated.

You have it right. For most installations with 1x SRAM mountain cranks, the -6mm offset is for 135 QR and 142x12, and the -3mm is Boost aka 148x12.

The "most installations" qualifier is due to the various asymmetrical rear end designs out there, like for example Cannondale's Ai. Bikes like that shift the cassette over by some amount, so the rear chainline is wider than it would be. That is one instance where what you have could be the right thing even on a 142 bike.