tiny amount into the 'free' xp pot.
5% iirc.
Try not to use your free XP unless you really need to. 16k sounds like tier 5 to 6 and there are much more potentially painful grinds. Try to use it for modules and not the next tank; you realy need XP for tracks on some tanks just so you aren't using a joke gun at stock. If you have enough tanks to play instead just save that final grind for daily's. I have a fair few stinkers and arty which I just do doubles on.
Evil was ninja'd me
I skipped the end of the AMX40 too and the somua was got awful.)
)