The problem is the wording in the SFA Judicial Protocol. It says 6 booking in 19 matches merits a 1 game ban, 12 in 38 a 2 game ban and 18 in 38 a 3 game ban.
What is unclear is whether that means the first 19 matchdays - then the threshold raises to the 12/38 (similar to in England), whether its the first 19 appearances or whether its a rolling 19 matchdays from the first booking.
I had a look at Scott Brown's record last season. He received his 6th league booking of the season on 6 Feb at home to Hibs. Unless the threshold is worked as in England (6 bookings in the first 19 matchdays) then he should have served a suspension. He didn't. He was sent off 10 days later and served a 1 game suspension and, despite 2 further league booking in the remainder of the season, was never suspended again. That leads me to believe the threshold resets to 12/38 after matchday 19. Others disagree. I've emailed the SFA but no answer yet.
Player stats of Scott Brown (Karriereende) ➤ Goals ➤ Assists ➤ Matches played ➤ All performance data
www.transfermarkt.co.uk