T and S are the flux ratings (T is brighter than S). WA in both cases has to do with the color (search chromaticity diagram). K is the forward voltage rating (increases with the alphabet).
I *think* the first figure, 67.2 lumens, is the max output@700mah, the second is the max output@1000mah. The Lumileds datasheet doesnt make it completely clear, it quotes 60 - 65 lumens@700mah and just gives one figure of 80 lumens at the higher drive level.
I remember this subject has been briefly touched upon before, but damned if i can find the thread.