Checkboxes – I am doing it wrong

I am having a hard time understanding the checkboxes fieldtype, and I believe The Lodge can help me figure things out :)

This is in my fieldset:

objectives:
  display: Objectives
  instructions: "What objectives does this page aim to solve?"
  type: checkboxes
  options:
    o1: "1) Objective 1"
    o2: "2) Objective 2"
    o3: "3) Objective 3"

In my page, the output is:

objectives:
  - "o1"
  - "o2"

And I want to output this:

objectives:
  - "1) Objective 1"
  - "2) Objective 2"

Should I use the checkboxes fieldtype for this, or is there another way to do it?