GVWR...Gross Vehicle Weight Rating----max amount the truck can weigh based on MFG ratings
Payload/Cargo Carrying Capacity----max amount of weight that can be added to truck (passengers/stuff etc) ---weight that truck can carry
MAX Tow Rating.....Max weight truck can tow
GCVWR...Gross COMBINED Vehicle Weight rating---max weight that truck and trailer can weigh together
Your 2008 F350 can weigh when fully loaded up is 11,500# (GVWR)
Your 2008 F350 and a trailer can weigh up to max of 23,000# (GCVWR)
Max Tow rating of 15,200# is the amount of weight truck can tow with a 150# driver and 20# cargo provided truck doesn't weigh more then 7800# (GCVWR minus truck weight equals max tow rating)
You will run out of payload/cargo carrying capacity long before you reach that 'magical mfg marketing max tow number'