I don't think anyone would intentionally pick an ILL timeslot that doesn't fit with their plans for that day but with the way the times jump around when purchasing ILL in the morning someone could originally choose 10:00am, for example, as their timeslot but by the time they've gone through the check out process it could have jumped to 6:00pm and then that's right when they have a dinner ADR scheduled or something. The easy solution to that though is to just go to guest services and explain what happened and ask them if they could change it.