Osmolality is a measure of the osmoles of solute per kilogram of solvent (osmol/kg or Osm/kg).
This is all part of the conspiracy to make me feel stupid. ;-)
Don’t feel bad, LOL, I had to dust off an old book and look it up.
Tomorrow, I would need to pull out the same book and look it up again.
If the solution weighs 1 kg/liter they are the same anyway.