Is this a notice from your payroll department? I suspect that "PP1" and "PP2" means "Pay Period 1" and "Pay Period 2" respectively. Also, "PRV YTD SDI" is "Previous year-to-date SDI."
As an NJ resident you should be having NJ tax withheld, not PA tax - reason being that NJ and PA have a reciprocity agreement that allows residents who live in NJ and work in PA to pay only NJ tax - and vice versa. See:
Income Tax - PA/NJ Reciprocal Income Tax Agreement - NJ Taxation
It references a form to fill out for your employer so that they will withhold NJ income tax, not PA tax.
As for SDI - I'm not 100% sure on this, but I believe that SDI is NOT part of the reciprocity agreement, and hence you pay it to PA since that is where you work. But you may want to ask your payroll department.