Skill edit potion

How much can I delevel if I buy that ? (28 Silk)
I dunno how that works..

Should be 5 no? But why does it costs 28 silk, what I get as a bonus? :p

5 levels , upgrades of any skill, mastery u added (28 silk)
the bonus is u gain 100%of your sp back while curset hearts give u 80% of sp back

kind regards

Someone write that's it's moved? :P