Help me understand my eyeglasses prescription

I have a prescription for my glasses. I should be getting bifocals, but I can’t afford them. The last time, I managed to get two different types - one with my distance prescription and one for close-up. I lost my close-up glasses, and I don’t know how to order a replacement pair from Zenni Optical. Here’s my prescription:

                     (SPH)         (CYL)        Axis           NV-ADD
OD - Right     -3.50          -1.00         60
OS - Left       -3.25          -1.00         75
           PD        69

Do I subtract the NV-ADD number from the SPH value? That would make the right eye SPH -1.50 and the left -1.25?

Yes, I know I should buy from my eye professional, but I just don’t have the money. Please help.

Cool, thanks.