What is this yml construct?

Question

Spring

one:
  two:
    three:
      four:
        "[some.property]": true
      five:
        "[some.another.property]": true

Interested in the design for four and five.
"[some.property]": true
Is this a map that has a String key "[some.property]" and a Boolean value ?
If so, do I understand correctly that in order to add another entry to the map, you need to do this:

four:
        "[some.property]": true
        "[another.property]": false