A trip is a one-way ride, so assuming you make 2 trips a day over the 10 days, you'll be taking 20 trips.
From filling out the schedule request for NYPenn and Rahway on NJTransit's website:
There doesn't appear to be any particular discount for a Ten Trip ticket, since the regular one way fare is $9.25, and the Ten Trip is $92.50. The Ten Trip seems to be geared towards people who occasionally need to travel the route and can save time by buying multiple trips with one purchase.
A combination of a Weekly pass ($82.50) and a set of one way tickets (6? x $9.25) to cover the remaining days might be a better deal if one needs to travel regularly for a short period of time. ($82.50 + $55.50 = $138)
From NJ Transit website - Ticket Options
Unlimited trips between two rail stations from 12:01 a.m. Saturday through 6:00 a.m. on the following Saturday. On sale beginning Thursday and continuing through Tuesday. Rail weekly passes can also be used on light rail or bus.
The following is just an example of scheduled trains for this morning. The Rahway - NY Penn track is covered by two lines, North Jersey Coast and Northeast Corridor.
Just a caveat on buying tickets. There may be an extra charge if you don't get the ticket prior to boarding the train. (Bolding emphasis mine.)
Ticket Purchases On-Board Trains
You can purchase tickets aboard the train without penalty only if there is no ticket agent or ticket
vending machine available (A $5 surcharge is applied to tickets
purchased aboard trains if a ticket agent or ticket vending machine is
available at time of boarding). Customers with disabilities and senior
citizens (62 or older) may purchase tickets aboard any train without
penalty. Conductors cannot accept bills larger than $20.
Fares are current as of August 2018. Fares may increase in 2019 depending on state budget negotiations. NJ.com article