Help with most recent value

[Shock]

Hello,

I am trying to select the most recent value for gallons from the test table. I keep ending up with the max value instead of grabbing the most recent gallons value. I have tried a couple of things with the same results

ANY(
SELECT(
Test[Gallons],
(
[_ROWNUMBER] = MAX(
SELECT(
Test[_ROWNUMBER],
([_THISROW].[Test ID] = [Test ID])
)
)
)
)
)

also tried 

IF(MAX([Related Test][Date]) = True,MAX([Related Tests][Gallons),"")