Nik, I did some 7* training on NordGems/Academy and wrote it on a piece of paper. I think it showed a reduction of around 30-33% from previous star (which, I think, merely confirms what others have posted before) but.....

...do you know where I put the bit of paper? >.<

(Wolfie is now going to slap me for not immediately putting it in OO Calc like I should have. )