As I understand it, he receives an automatic promotion to Sergeant because he joined Special Operations (this is based on the Starting Rank entry for the Career on page 32). He's then able to make a normal roll.In the character creation example on page 39, "step" 5:
Clark enters Special Operations. He is promoted to
Sergeant, increases RANGED COMBAT to C, and gets SURVIVAL
D. He makes another RANGED COMBAT roll and succeeds
again! He rolls 1 and gets the Paratrooper specialty. He
is promoted to Staff Sergeant and his CUF increases to
B.
Is there a reason why the example character is increasing his rank twice during this step?
If he had been able to become an Officer in Special Operations, his rank would jump to Second Lieutenant with a chance to promote to First Lieutenant.
Does that help?