Getting knee motion back after surgery is called mechanical recovery. Being able to perform your daily activities or get back to sports is referred to as functional recovery. What you are noticing is the lag between mechanical and functional recovery.
Such a difference is fairly common. There are many possible reasons for this. Regaining motion is just one part of recovery. There's also muscle strength and joint position sense (proprioception) to consider. Your rehab program will include exercises to help with motion, strength, and proprioception.
Your doctor and your therapist should be able to give you some idea of what to expect over the next weeks to months. They will likely base their predictions on your age, condition before surgery, and compliance with rehab. They also have the advantage of seeing the results of many patients who have come and gone before you.