Not super familiar with this example, but...
NewHTTP() and PostFromStringWithTimeout() are not SDK functions. They're defined in BrightScript somewhere in your channel. You need to find that code, look at what it does with the parameters you're passing, and modify it to do what you want.
The first place I would look is the call to Prep() and the value (if any) assigned to the callbackPrep attribute.
Function http_post_from_string_with_timeout(val As String, seconds as Integer) as String
m.Prep("POST")
if (m.Http.AsyncPostFromString(val)) then m.Wait(seconds)
return m.response
End Function