Unlearning times for partially learned skills get longer instead of shorter as you learn more.
e.g. Right now I am learning Piety and I'm about 80% of the way there. Because Piety has a base time of 24 hours, the time to unlearn it with Unlearning 3 should be 4.8 hours. One would expect, that to unlearn the partially learned skill would take about 80% of that, or nearly four hours. Instead, it takes 20% of that, or a little less than one hour.
To verify this, choose a skill to learn and check the unlearning time immediately after. Wait a few minutes and then check the unlearning time again and you will see it has gone down rather than up.