Employee stated EE and EE's bolt partner just finished putting up the first row of bolts in the #4 Left entry on the Unit 1 Section. In the process of sitting in the operators compartment of the roof bolting machine a rock which measured 30 x 18 x 2.5 thick fell from the mine roof and struck the employee in the right hand. This caused a laceration and EE received 6 stitches.