After 18 days I reckon you're fine.
I did a couple of private ones before my first. I reckon it takes a day each 0.1, from a 'sozzled' 3.0% saturation to a baseline 1.0%. Which would put you in the safe zone even if you were totally bollocksed.
The danger is how quick the percentage goes up. The 1.7% is 'average', so whatever that is. But I reckon a moderate weekend could see you up above 2.0%, and even just one all-dayer could put you at 3.0% from nothing straight way.
Units go quickly. But the effect on CDT is a slower mend. And it totally explains why you can't think, exercise, or even breathe as well the day after a heavy night, and why I really don't drink a lot now.
But remember it isn't just your CDT result they will go off. I got asked loads of questions about what I drank, before I even stopped drinking. Your CDT could be low, but if you say you binge, you're ****ed. Someone I indirectly know was failed for being too honest.