Atomic Structure

For s-orbital, l=0
For d-orbital, l=2
For f-orbital, l=3
For, f-orbital m1 values can be −3,−2,−1,0+1,+2,+3
So, 4f can have ml=−2
Each orbital with ml=−2 can hold 2 electrons.
Orbitals that can have ml=−2 are 3d,4f and 6d
Total electron =2+2+2=6