3 items - Reduce cost of spells by 3%.
5 items - Adds 15 Magicka Recovery
I realized that the bonus "reduce cost of spells by 3%" is cumulative, that means each piece that I put, my skills cost 3% less. However, the bonus "adds 15 Magicka Recovery", although I am using 6 pieces, not accumulates.
This is a bug, or was meant to be like that? How should I know before testing, whether a bonus is cumulative or not?