Subtotal for measure calculating changes over time using date slicer

Hi everyone,

I'm currently using a data set that takes a daily snapshot of my data and appends it to the table. 

An example of my data is this (create date is the daily snapshot date):

The matrix displayed in the power bi visual is the change of volume between the two dates selected on the date slicer.  The delta is calculated with the following measures:

First Date = CALCULATE(MIN('date table[First Date]), ALLSELECTED ('date table')) 

QtyFirstOrdered = SUMX(FILTER('QtyArchive', 'QtyArchive[CreateDate] = [First Date]), 'QtyArchive'[Qty - Ordered]) +0

-Same method is used to calculcate the last date quantity ordered (replace MIN with MAX in first measure). 

QtyChange = [QtyLastOrdered] - [QtyFirstOrdered]

At this point, everything is calculating as expected.  I'm running into issues when I use the measure for QtyChange in other formulas.  Example:  I need to only Sum the negative qty changes.  I've used the following IF statements in measures, and both are correct on a row level, however the column subtotal at the bottom of the matrix is 0:

= IF([QtyChange]<=0,[QtyChange],0)

= IF(QtyChange]<=0,SUMX('QtyArchive',([QtyChange])),0)

What is my measure missing to properly subtotal the negative changes and then continue to build upon the [QtyChange] measure?

Thanks!