Did you reach sage of six paths before? If not, you will only get the minimum reward.

After you reach it for first time, every next month you will get rewards according to the rank you managed to achieve in certain month. Before that- you will get just lowest reward.

Well that's how the system works. The system wants you to get six paths first. If you read the instructions, it will tell you even though it is not in simple English for basic understanding. It also tells you in your mail.

I assume you're on a relatively new server since you seem to be new and are asking rookie questions. If you can, try to get to six paths before your server gets to cross server (about 2 months when your server opened) as it gets harder once your server is cross server. However, that will be hard for a f2p, so take your time moving up if you plan on playing for a while.