From reading my own data, (at a guess) I think QLN is a shortening of Qualification Start Date. ASMT is confusing. Possibly Assignment Year Start Date?

My most recent entry has 2Oct23 in the QLN column, which is the date I reached gold. ASMT is 9Oct22 is the start of the tier point year I achieved that in (and indeed all other dates in that column are 9Oct - my TP reset date)