Enough to hold bone
Depending on what was used to fix your tibia, screws should engage the bone.
Usually the tip of the screw may protrude a few millimeters. Because the tibia is a subcutaneous bone in certain areas (it is right under the skin), sometimes the tips of the screws can be symptomatic. After your bone is healed, you can discuss the appropriate time to remove screws if they are symptomatic.