The scores translate to: 

A =  Most likely to convert

B = Most likely to convert

C = Likely to convert

D = Less likely to convert

E = Least likely to convert

X = Not found in COOP (Non-Profit Cooperative Database)

If your Philanthropic TAG score includes a number, the number ranks that specific score; 1 being the highest. 
Example: A patient with a score of B1 is more likely to convert than a patient with a score between C-E as well as B2 or B3.