The K: must be the last item in the header, because abc treats anything after that as the notes of the tune.

Putting a meter in M: will set a default note length, which a following L: can change. Putting them the other way round may not always have the desired results.

The recommended order is therefore: X: T: M: L: K: If you use Q: to set the tempo it is best between L: and K:

If a tune has alternative titles you can have additional T: lines, thus:
X:1
T:Danny Boy
T:Londonderry Air

Wassail! V