So you own a Galaxy S4, Tab 4 8.0 LTE, or Avant and have just received an over-the-air update from T-Mobile. What does it do? Regardless of which of the three devices you own, the answer is the same: not much.
The Galaxy S4, easily the most popular gadget of the three, is receiving a bump to version M919UVUFNK2. This brings with it Chinese language support. Don't speak Chinese? Proceed not to care about this update. The same is true for Avant owners, as the G386TUVU1ANK3 update you're getting hit with sports an identical changelog.
The Tab 4's update to T337TUVU1BNK4 brings software stability improvements. If you felt your experience was already pretty rock solid, then carry on about your day.
On the off chance that one of these updates really did catch your interest, you can read up further at any of the source links below.