If the grenade fuse has been set to less than 4, because the enemy is closer to Torque than four spaces, then Torque does a scan relative 1 instead of scan forward. This is because if there is an obstacle between 2 and 5 spaces in front of Torque, it would be picked up by the scan, but the enemy would still be damaged when the grenade crashed into the obstacle. The only thing that Torque needs to check is that the space directly in front of him is empty, so that the grenade does not explode too close.
In the example, Torque is shown in the green box and the enemy is in the blue box. The enemy will be damaged when Torque launches a grenade, regardless of the value of the grenade fuse.