For example, 8²₃ means... - The crossing number of given knot(s) is 8. In the other words, when you put the knot(s) to the flat floor, there are 8 crossings.

For example, 8²₃ means... - The crossing number of given knot(s) is 8. In the other words, when you put the knot(s) to the flat floor, there are 8 crossings. - There are 2 independent knots there. They are colored differently so you can easily see this. The collection of knots is also called a link. - The subscript is numbered in the predefined arbitrary order starting with 1. There are many different knot notations, but this particular one is called Alexander-Briggs notation.