Green’s Dictionary of Slang

about right adv.

to the best extent possible.

[US]Albany Microscope (NY) 9 Mar. n.p.: He flatters himself that things will work about right.
[US]Manchester Telescope (NH) 10 Feb. n.p.: It does up the thing about right on the loafers who stand on the corners to watch the girls.
[US]Life in Boston & N.Y. (Boston, MA) 8 Oct. n.p.: Miss Allen [...] showed her legs ‘about right’.
[UK]Hotten Sl. Dict.
[UK]J. Ware Passing Eng. of the Victorian Era 209/1: Right, About (Peoples’). Modest self-depreciation, or depreciation in general; not absolutely right, but nearly so, e.g., ‘I thrashed him about right’.