PLSC 480, 490 and 491 all carry course credit, which means these courses are treated like any other when it comes to calculate distinction. For example, if you receive an A or A- on your senior essay in PLSC 480, your grade on your essay is also your grade in that class. This course then counts as one A grade and one course credit toward your total number of courses for distinction purposes.
This is also true for PLSC 490 and PLSC 491. If you earn an A or A- in PLSC 490 and 491, which each carry one term course credit, you will receive 2 A grades and 2 course credits toward your total number of courses for distinction purposes.