Sounds like your goal and time frame might not be set correctly. Try setting a smaller goal for six months. For me I set a goal of 50lbs in 6 mnths. I need to loose more than that. Losing 1-2 lbs is safe and healthy.
I've just set up & I have the same prob. Mine is saying my daily allowance is only 390 calories per day! I cannot find a way to change it anywhere in the settings??
I think your minus means you've gone over your daily allowance (which is set in the bar on the opening page eg: mines 1500 a day) and if I go over that, it says I have minus amount left - so you need to exercise to burn some off.
If you keep going over your daily allowance, they will keep adding up and up so you won't lose as much weight as the app suggests. Try and see how many cals your allowed on a daily basis and stick within that amount, the minus figure should then come down and equal itself out over a few days...