I think it's more like this, no?
2013-07-07: Batch 6 ordered - Expected date of arrival (10 weeks) - 2013-09-15 ---> + 15 days
2013-06-13: Batch 5 ordered - Expected date of arrival (10 weeks) - 2013-08-22 ---> - 10 days - refunded - 2013-09-01
2013-05-27: Batch 4 ordered - Expected date of arrival (10 weeks) - 2013-08-05 ---> - 28 days - refunded - 2013-09-01
2013-05-23: Batch 3 ordered - Expected date of arrival (10 weeks) - 2013-08-01 ---> - 32 days - refunded - 2013-09-01
2013-05-18: Batch 2 ordered - Expected date of arrival (10 weeks) - 2013-07-27 ---> - 36 days
2013-05-11: Batch 1 ordered - Expected date of arrival (10 weeks) - 2013-07-20 ---> - 43 days