Rest API runTimeInfo Timezone

Hello support,
We are trying to use the API endpoint rest/v3/servers/<guid>/runtimeInfo to get a given server's timezone and local time. We are generally able to use the ‘timeZoneId' value in the response to get the IANA timezone and derive what we want from that. This works across many accounts, but for a single account we are getting contradicting values in the API response. For example, one server has 'UTC' as the 'timeZoneId', but the 'timeZoneOffsetMs' value is -14400000 which maps to the EST timezone. Generally however we see the 'timeZoneId' to be America/Detroit when the 'timeZoneOffsetMs’ value is -14400000.

Can you please provide more explanation as to which of the fields to use and why sometimes they are synonymous and sometimes unrelated?
Additionally, we see the 'synchronizedTimeMs' and 'osTimeMs' fields. Can you explain what these fields represent as well?
Thank you,
Elan