My understanding is that it means something like 60 days were put on - horse doesn't try to buck rider off, knows walk/trot/maybe canter and a little steering. Not much work was done with horse, either - so maybe started 30 days, rest for a month or two, then 30 days again - something to that effect.
Depending on the person saying it, somewhere between 'it's been sat on twice 6 months ago and no one died' to '60 days of real basics, maybe some w/t/c, steering, but not confirmed.' It might have only been ridden on the lounge line and it might never have cantered under saddle. It's basically between backed and green broke.
I had a horse that had maybe a dozen rides on her one fall, left for the winter, and maybe a dozen rides in the spring when I listed her for sale. You could walk, trot, sometimes canter, steer, and she was very willing, but greener than green. I advertised her as lightly started under saddle (she'd also had a couple of years of driving under her belt and had gone to some driving shows, so it was also a distinction from that, where I would have considered her quite experienced).