Up until BRENO, you are in LECB, LFFF, and LIMM airspaces. All of these airspaces use a North-South rule for cruising altitudes, where northbound flights should use even altitudes.
Between BRENO and GAVLI, you are in LOVV, EDUU, and LKAA airspaces. These use an East-West rule, where eastbound flights should use odd altitudes.
After GAVLI, you are flying on the T203 airway. This airway uses even altitudes when flying in that direction (image from the German AIP below):
Haha, leave it to Eurocontrol to hide this inside of a “Utilization” word-salad column. Not like Annex 3B doesn’t already exist for exactly this purpose, it even has a dedicated column to define even/odd levels..
SimBrief can automatically parse Annex 3B, but there is very little chance that Annex 2B will be auto-parsed any time soon. So this is to be expected at this point unfortunately.
I’ve amended this specific route at least, for whatever it’s worth.