List
A list is a way of sending multiple values for a single property.
In this case, the values are placed together in a single piece of text, with a symbol (usually a '|' symbol) separating them.
For example, if you'd like to send three numbers in a set called 'ladder', and separated by '|', you'd use the following…
ladder="0,10,30"
An alternative way of transmitting many points is through a Set.