Base levels, plus what each job reaches at four condensing stars (light cells). The top level is 10.
LumberingLv 3 out of 10→ 6★4, Lv 6 at four condensing stars
CoolingLv 3 out of 10→ 5★4, Lv 5 at four condensing stars
Condensing raises its jobs like this:
★1 +1 Lumbering
★2 +1 Cooling
★3 +1 Lumbering
★4 +1 to every job
Condense it at a Pal Essence Condenser (unlocks at Lv 14) using 4, 8, 12 and 24 more Reindrix for each star (48 in all). Or feed it Starfruit ☆1 to ☆4 from the Medal trader, or a Ripe Starfruit from the Bounty token exchange. The Condenser shows the new levels before you confirm.
The game picks the drop list by level: a wild Reindrix at Lv 70 or higher uses the World Tree list instead of the normal one, and at Lv 80 the Aura list. World Tree farming guide