if i make a list of 3 elements and add one more
  - how long is the new list?
=> 4 elements

if i have a list of 10 elements - how long is it?
=> 10 elements

if i have an empty list - how long is it?
=> 0 elements

if i have an empty list and add 3 elements - how long is it then?
=> 3 elements

if my list has 5 elements and I then add 3 elements - how long is it finally?
=> 8 elements