As @success01 has said, I think the back order is exactly how it...

As @success01 has said, I think the back order is exactly how it sounds - it's the number of IQbuds that Brookstone have ordered. 252 must be some predetermined amount they arrived at during their sales forecasts, which was adequate until Unbox Therapy got involved.

It's not necessarily coming in one delivery either. There was also 252 units on back order this time last week. When Brookstone entered 108 new stock into their webstore on June 14, the back order amount was then showing as 144. Almost immediately upon selling out yesterday, the back order was back at 252.

Nuheara also entered 612 units into their warehouses yesterday evening, which I believe is what was leftover from the latest Flex delivery, after distributing to their retail partners. This was somewhat confirmed when Best Buy received new stock this afternoon, after running out early this morning.