AWS Mediaconvert: Styling in VTT captions

Hi,

I noticed that there are many properties that are standard to VTT captions but are getting ignored by mediaconvert when doing the burn-in captions for videos. As an example, the timestamp tag (details here) used to define karoke style captions (where words appear at the right time) is note getting considered. It is making no difference to the output. Is this not supported?

Also, any type of styling like 'font-family' information is making mediaconvert to ignore the whole caption file. No captions appear in the output if I specify this (example below). Is there any place where I can read what style options for VTT files are supported & what is not supported? I need it so I can only use the Style options that are supported.

WEBVTT

STYLE
::cue(#\1) {
  color: red;
**  FontScript: monospace;**
}

0
00:00:00.009 --> 00:00:02.819
You can add a <b>subtitles by using the mediaconvert jobs.</b>

1
00:00:03.279 --> 00:00:06.650
As soon as the <00:04.500>video is generated, <00:05.500>it is available for use