Green’s Dictionary of Slang

(US) extremely, at the maximum, at most.

1907		C. Fowler letter 16 Aug. in Tomlinson Rocky Mountain Sailor (1998) 258: He seemed to have tired of the game by this time, for it took him only about three minutes Max to administer the oath to the both of us .
1956		J. Thompson ‘The Cellini Chalice’ in Fireworks (1988) 76: If you can bank me for two-grand max, I’ll guarantee —.
1962		P. Anderson Time & Stars (1966) 88: Four days max, then, to get them to safety.
1977		in Texas Monthly Feb. 152: The first in a series of posters would be ready in ‘six weeks max’ [HDAS].
1983		C. Heath A-Team 2 (1984) 118: Half an hour ago, max.
1991		C. Hiaasen Native Tongue 23: The batteries last about two hours max.
2000		P. Beatty Tuff 182: I think you’ll get four months max, maybe a fine.
2002		‘Valley Girls’ on Paranoiafanzine 🌐 And I’ll even show you how to be a maximum warm babe like us how to get a totally viscious dude to notice you.
2009		P. Temple Truth 21: I’m on my way. Twenty minutes max.
2018		G. Gilmore Class Act [ebook] ‘We have to find him in three weeks max’.
2023		R. Milward Man-Eating Typewriter 33: Off the alcool (healthier if not maxi well nourished).