I can't split mastery point in tier 1, 3, 5 in mastery page using the new alpha client

When I am setting my mastery page in the new alpha client (under collection section), I can't split the 5 mastery point from tier 1, 3, 5. I could only choose all left or right side with all 5 points put in 1 of the 2. anyone else who find the same problem too? Thanks.