when rating is null, what the meaning and how to use it?

[LeopoldACC]

@peterjdolan @agnoster
Thanks for your sharing of your work.
I found that some process of solution's rating is null, like below.
How should I use data like that?

{
      "completions": [
          {
              "text": "Now I can use the property that if two powers of the same base are equal, then their exponents must be equal as well.",
              "rating": null,
              "flagged": null
          }
      ],
      "human_completion": null,
      "chosen_completion": 0
  },
  {
      "completions": [
          {
              "text": "So I have\n\\[-\\frac{3}{2} + 2 \\cos \\theta - 1 = \\frac{1}{4**} + \\cos \\theta - 1.\\]",
              "rating": null,
              "flagged": null
          }
      ],
      "human_completion": null,
      "chosen_completion": 0
  },
  {
      "completions": [
          {
              "text": "Simplifying this equation, I get\n\\[2 \\cos \\theta - \\frac{5}{2} = \\cos \\theta - \\frac{3}{4}.\\]",
              "rating": null,
              "flagged": null
          }
      ],
      "human_completion": null,
      "chosen_completion": 0
  },
  {
      "completions": [
          {
              "text": "Subtracting $\\cos \\theta$ from both sides, I get\n\\[\\cos \\theta - \\frac{5}{2} = - \\frac{3}{4}.\\]",
              "rating": null,
              "flagged": null
          }
      ],
      "human_completion": null,
      "chosen_completion": 0
  }