Eligibility is an academic year measure, not a semester measure.
For example, Sam Cunliffe.
Played Fall Semester 2016 for ASU, then transferred to KU.
One year of eligibility used.
Sat from Jan-Dec 2017 due to transfer rules.
Played Spring Semester 2018.
Two years of eligibility used in his two years of college, but due to transfer rules he only played for one.
Note that the rules are 5 years in which to play 4 years/seasons.
Sam has now used 2 years of eligibility in 2 years of college, so he has 3 years left to play 4.
Yes, he could still redshirt a year if he wanted to do so.
Similarly, playing this semester will count as one year of eligibility used for Silvio.
These are the current rules.
I believe the rules used to be different (e.g., see the case of JoJo White), but I do not know when they changed.
"Travel is fatal to prejudice, bigotry and narrow-mindedness, and many of our people need it sorely on these accounts. Broad, wholesome, charitable views of men and things cannot be acquired by vegetating in one little corner of the earth all one's lifetime." - Mark Twain "Innocents Abroad"
