okay, so if my rx is:
od -3.25 cyl. .50 axis 55
os -3.50 cyl.50 axis 55 add 4.00
so then if i'm understanding this right, the 4 is subtracted by my rx and my actual add on my glass would be 4.00 - "3.50"my lens power?? is that right or am i totally screwed up/!