στη before μ
Actually it is στην, but it sounds like στημ because of the following μ.
Mmm, I think Phil means it should be στη instead of στην (the final -ν rule). I think we corrected that, στη is accepted now. ^.^
Does it really mean that both στη and στην are correct? Why?
Yes, if στην is not followed by κ,π,τ,ψ,ξ,γκ,μπ,ντ,τζ,τσ you (can) ommit the -ν. So, both are correct.