Base on his value, he should be a fast trainer. Would you give him some more training to see if % progress increase? 172% for 3 training is a bit low, he should reach around 240% (40+80+120% average).
1Q increase 5% player value approximately.
15SP = 1Q so if you singed 6SP mean he is increase 0.4Q exactly
0.4Q = 2% his value = 1.37 x 2% = 0.0274M
after singed 6 SP your player value is 1.37 + 0.0274 = 1.3974M correct??
Still thinking your player should train faster..