This is convoluted...I think this is what I saw...
* Seattle (#57) trades down with Detroit 18 spots into the mid third (#75).
* Detroit coughs up their mid 4th rounder (#107).
* Seattle (#157 and #209) and Detroit (#154 and #205) swap 5th and 7th round picks, Seattle jumping up a few picks in each instance.
According to updated draft value charts, Seattle lost about 32 points on that trade...about the value of a late fifth-rounder. Detroit should have just coughed up their fifth entirely. Oh well.