There is no Medicare Premium on the 1099R Box 11.  Medicare Premiums are deducted from your SSA-1099 from Social Security.  You will need to go to the SSA-1099 Social Security screens to enter the Medicare Premiums paid.

You can get there by going to Search then entering SSA-1099.  You will be offered a "Jump" function to take you to the SSA-1099 input screens.