It would mean he's eligible for 2018, 2019, and 2020. How to label each year of his career, I'll leave to the experts.
Caveat that he can't apply for the 6th year until after the 5th year (after March 2019). So we won't know officially until the NCAA rules.
I'm interpreting this as the coaches being confident, but as NoVa said, the NCAA is predictably unpredictable about such things. Just ask Aaron Anspach -- or better yet, don't.
Maybe this is just setting up options. If Cassar gets 6th year, Beard grayshirts, redshirts, starts as a RS FR. If Cassar is done after 5, then Beard grayshirts and starts as a true FR but with a year in the room.