Help!

According to the weight loss tools here, I should restrict my calories to 1300-1400 per day to lose from 140 to 115 lbs. BUT, if I want to maintain 115 lbs, I can raise that limit to between 1600-1700. That seems like a contradiction to me. If I need to be at 1300 to get there, why would I not have to keep it at 1300 once I'm there?

You lose weight by creating a deficit from how many calories you burn now (at your current weight of 140), usually around 500 calories per day for a 1 pound per week loss (although the site doesn't want you to go below 1200 if you are an adult woman).  Once you get to your goal weight (115) the site calculates that you will need 1600-1700 to maintain that.  These are all estimates, you may be more (or less) active physically, you may have more (or less) active muscle tissue, there are also slight variations in metabolism rate.  Once you see how your weight loss goes you will have a better idea of what you need to do once you are maintaining.

Yes - Weight loss and Maintenance are two very different goals. The 500-1000 caloric deficit is specifically geared towards you losing the extra weight (maximum of 1000 calorie deficit/day is seen as healthy. And women should eat no less than 1200 calories per day to be at a healthy consumption level). But when you reach a healthy weight, obviously you are not going to want to go below that so eating at a deficit has to stop. So at this point you shift from a weight loss caloric allowance to a weight maintenance caloric allowance. Hence the increase in number - which does not translate into weight.

Hope that is helpful!