Both are maximum torque specs that were originally called out in inch pounds (55 and 120, respectively) and converted to Newton meters. Your wrenches are both under the maximum torque spec, so you're not in too much danger of breaking anything from over tightening. I'd use carbon paste in the seat tube. If the saddle creaks at the clamp, I'd search for a torque wrench that maxes out at 15-16 N-m.