yep. don't expect to be going upwind sub 16 knots at all on a 10m for some time. if you have current with wind of 4 knots that explains why the 18 knots low end.
ps light wind skill takes time to build. don't expect to be matching your more experienced buddies for some time. As a newbie you will need power to crank upwind.
pss 10-15 knots typically requires a monster kite and then its still pretty boring. the fun really starts +16 knots on the water.
13 to 15 for me man, at 75kg! Fun as!