The cost calculation does not include netting. On the day itself you cannot say whether or not there will be netting. Only over a whole year can you see whether more has been supplied back in a whole year than has been consumed. That is why you see a calculation without netting. The amount you feed in is multiplied by the high and low tariff you entered for electricity feed-in. If you enter the same amount there as for the electricity consumption tariff, the costs will look like you are netting. This works well if you feed-in less than you use in a whole year.