They probably simply haven't caught up with demand yet. There has been a lot bigger demand for Tether since around January when the Bitcoin price spiked. That is the risk with a centralized coin like this though.
There is no sure way for them to "catch up with demand." They are supposed to have 1 USD in reserve for each 1 USDT. There is no place for this $11 million USD to come from. I wonder why the price still holds at 1 USD and does not collapse?
I believe that this is a result of the drop in the value of BTC last week. The only option for them seems to be to not issue anymore USDT until the price of BTC catches up (assuming it does so).
EDIT: After more research apparently (although it is not explicitly stated) they only issue USDT per USD they receive. And vice-versa. So they can exchange as much BTC for USDT as they want, and can take a gain or loss on it, but it should not affect the reserves, thus they should be able to maintain solvency. They are not/do not have a bank, but store the USD in external commercial banks, so the funds should be relatively well-protected. There is always the risk that the company absconds with the money. Tether is incorporated in the Virgin Islands. There is some concern that the founder, Brock Pierce, was involved in a child sexual abuse ring:
https://www.buzzfeed.com/hunterschwarz/mystery-man-at-center-of-alleged-hollywood-sex-ring-has-vani