Hi Lawrence,
With the Plus Dining, you will receive one Table Service, one Quick Service and one Snack credit per person, per night of your stay. You can use those whenever you want (it doesn't have to be one sit down meal per day). For example, you can eat 2 big meals on one day and 2 quick service on another.
If you want to choose some of the Signature Dining restaurants, just know that those require 2 Table Service entitlements per person per meal. In that case, you would be eating one fewer meal, as you'll have used up 2 credits at once. For this reason, when my family chooses to eat in one of those restaurants, we pay cash.
Due to the popularity of Disney's fantastic restaurants,
reservations are strongly recommended. You'll want to browse the various
options
HERE and can call 407-WDW-DINE to book (or reserve online).
I purchase the Plus Dining on almost every trip, and am happy to answer any other questions that you may have. Simply send me a follow-up question.
Have a wonderful vacation,
Kaylene