reasonable window allowed for successful network response

I'm implementing the Play Integrity API.

In the integrity response there is timestampMillis, documented as:

The timestamp in milliseconds when the request was made (computed on the server).

I'll compare it to the current timestamp in order to know the freshness of the response, and to avoid/slow down hacking attempts.

The official documentation does not suggest the ideal allowed window to check it, because it may depends on various factors.

Without considering the case when the user's connection is slow or unstable, which causes an empty/failed response that I'll handle with an exponential retry, what should be the maximum time allowable for a success response?

I'm not asking for an opinion based answer but for an answer backed by some technical factors.

from reasonable window allowed for successful network response