OK, a little primer on Army ranks:
Enlisted men are all E-something - from the Private E-1 to the Sergeant Major E-9. Officers range from the O-1 Second Lieutenant up to the five-star general during wartime - not sure what O-rank that is, because I think some generals share the same number. Plus there's the Warrant Officers and Chief Warrant Officers, with their own ranking system.
Maybe this will help.
Entries listed in this form
Pay grade - Name of rank - Abbreviation - Note
E-1 - Private - PV1
E-2 - Private - PV2
E-3 - Private First Class - PFC
E-4 - Specialist - SPC or SP4 - For those not in a leadership position
E-4 - Corporal - CPL
E-5 - Sergeant - SGT
E-6 - Staff Sergeant - SSG
E-7 - Sergeant First Class - SFC
E-8 - Master Sergeant - MSG - For those not in a command position
E-8 - First Sergeant - 1SG
E-9 - Sergeant Major - SGM
E-9 - Command Sergeant Major - CSM
E-9 - Sergeant Major of the Army - SMA
O-1 - Second Lieutenant - 2LT - also called Butterbar

O-2 - First Lieutenant - 1LT
O-3 - Captain - CPT
O-4 - Major - MAJ
O-5 - Lieutenant Colonel - LTC
O-6 - Colonel - COL
O-7 - Brigadier General - BG
O-8 - Major General - MG
O-9 - Lieutenant General - LTG
O-10 - General - GEN
O-10 - General of the Army - GA - Awarded only in wartime
Warrant Officers occupy a strange grey area somewhere between Enlisted and Officer, but their technical skills put their deserved respect level somewhere well above the rest of us.