Isnt' there a final 500 charm one which has rainbow magatama? That's a old one based on date You have till 500 charms for rebate now. Total number of charms you would finally get is still 10 when you reach 500, At 500 you get a rainbow magatama level 5 also. There is a 250 checkpoint also..Dont remember the lower ones.

If you charms level are not level 3 you can do this rebate, or better wait I suggest to get the full rebate. Rainbow magatamas lvl5 are hard to get, so better to wait and go for full 500 rebate next month if you are a f2p or small spender.