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I was playing a good old one-off campaign tonight, and will be playing the same character through adventure league. I was playing a half-elf sorcerer, and my charisma modifier came into effect. I had rolled my stats, in the way it describes in the second chapter of the 5e handbook, and had gotten lucky with a 17. Half-elf adds two to that (19) and my proficiency bonus made it out to be +6. My DM told me promptly that there was no rolling involved with stats, and that it should be a +5.
This bugged me, so I stared at the page for 5-6 minutes, trying to find the lie. It says something along the lines of roll 4d6, and don't count the lowest number, and then rinse and repeat for 5 more numbers, and those are your stats.
Is this system still legal in adventure league?