I guess it all depends on the quality of work required. Some of the touch up can be done real quick with some tools, like erasing a bit of areola, or "whiting" an area (assuming by that, they do ask to simply put a white circle/square on the ko part), but yeah, toning down nipples or slimming down a model might require more work (though it also depends on several factors).
Having worked as a graphist myself in printing industry, this gives me flashback of one of my worst job where I was required to make adjustements for cards and expected to do nearly 250 a day. Thankfully, a good chunck of that was very minor stuff and in the end, only a bit over half actually require some "real" work, but yeah, you have do dedicate your whole day to that and learn to streamline with tools as much as you can, so you can do a job in just a few minutes. But yeah, sometimes, a work is so botched up to begin with you simply can't do it fast, or it'll come back to you later with a revenge.
The number of work and the deadline is still heavy, especially for a newcomer who they probably don't really know the level of skill, but at this point, it's obvious it's intended to be an absurdly demanding job.