Numbered lists are numbered wrongly

[HarHarLinks]

Describe the bug

sending

5. five
10. ten

gives

Reproduction

"content": {
    "body": "5. five\n10. ten",
    "format": "org.matrix.custom.html",
    "formatted_body": "<ol start=\"5\">\n<li>five</li>\n<li>ten</li>\n</ol>\n",
    "msgtype": "m.text",
    "org.matrix.msc1767.message": [
      {
        "body": "5. five\n10. ten",
        "mimetype": "text/plain"
      },
      {
        "body": "<ol start=\"5\">\n<li>five</li>\n<li>ten</li>\n</ol>\n",
        "mimetype": "text/html"
      }
    ]
  }

Expected behavior

Element does this which in my opinion is (at least/only) half correct by following the suggested start property of ol https://spec.matrix.org/latest/client-server-api/#mroommessage-msgtypes

Platform and versions

OS: Arch
Browser: 5.4.2763.3 (Official Build) snapshot (64-bit) 
Cinnyv2.1.2

Additional context

No response