converting played at from recently played

[Party-Size]

I'm passing over a UTC unix timestamp for one hour ago (for example if the current UTC timestamp is 1701203866000, I'm passing 1701200266000).  I played a few track 15-20 minutes ago, but they don't get returned.  If I set the time way back to say 1601203866000 I get the last 50 tracks from about 8am this morning, but still not the ones I played 15-20 minutes ago.

Is there a delay in how long it take for recently played to become available in the API?