At the shortest distance from a Gateway you might be using a high data rate (SF7) and under the policy above your limit is approx 12,500 bytes of data per day.
If your a long distnce from a Gateway you might be using a low data rate (SF12) and under the policy above your limit is approx 525 bytes of data per day.
You really need to plan for using low data rates unless you are really really really sure you are close enough to a gateway to use higher data rates.