Jennie is at seat 4 and next to Harvey and because Harvey has a higher seat(first info) so Harvey seat number is 5. Peter is across Harvey(2nd info) so His seat number is 1. Lia is next to peter(7th info) and can't be on 8(3rd info) so she is on seat 2. Kenny is next to Lia (5th info) so she is on seat 3. kenny's across seat is Rick(4th info) so Rick is on number 7. Joyce is not sitting on 8(3rd info) so she is sitting on 6. and the last seat is Mark's that is 8.
You are correct, it would be a reflection across the y-axis. I am great at visualizing but for those who are not (Not saying you) all they have to do is cut out a parallelogram and mimic the movements.
