I have an older VariX-2 2-7X33 that came with a used rifle I bought. I am having a hard time making adjustments because there is no click to the adjustments. It has marks on in for 0, 3, 6, 9, and 12, with 2 marks between every number. How do you adjust this scope, what is the adjustment marks mean is it in 1" increments for every mark at 100yds. Please let me know if you have any experience with these types of adjustments. I believe the scope was made in the mid to late 80's. Thanks