If the force is not exerted along the line of motion but is in some other direction, then the force can be split into two components: one parallel to the ramp and one perpendicular to the ramp. The component of the force perpendicular to the ramp will not affect the motion of the IOLab since it is perpendicular to the direction of motion. The component of the force parallel to the ramp will be responsible for the motion of the IOLab up the ramp.
If the IOLab is pulled up the ramp with a constant velocity, then the net force acting on the IOLab must be zero. This means that the force parallel to the ramp must balance the force of friction acting on the IOLab. Since the force sensor measures the force only in the y-direction, which is perpendicular to the direction of motion, it will not measure the force parallel to the ramp directly.
However, we know that the force parallel to the ramp must be equal and opposite to the force of friction acting on the IOLab in order to maintain a constant velocity. Therefore, if the force parallel to the ramp is not parallel to the surface of the ramp, but at an angle to it, then the component of the force parallel to the ramp that is measured by the force sensor will be smaller than the actual force parallel to the ramp. This is because the measured force is only the component of the force parallel to the y-axis, which is perpendicular to the force vector that is not parallel to the ramp.
In summary, the force sensor will measure a smaller force when the force is not parallel to the surface of the ramp, but at an angle to it, as compared to when the force is parallel to the surface of the ramp.