Shipment Manager Total Ship Unit Count is 1 greater that Order Release

I‘m fairly new to OTM. 

We set the values in Ship Unit 1 of an existing Order Release to zero. The Shipment Manager values reflect the changes made Order Release Ship Unit 1except the Shipment Manager Total Ship Unit Count field is 1 greater than the correct value in Order Manager Total Ship Unit Count . 

What is causing the Shipment Manager Total Ship Unit Count to be 1 greater than the Order Release Total Ship Unit Count and is there a way to correct this?

Here's the example:

Order Release has 3 Ship Unit lines. 

Line 1 Ship Unit Count = 19, Total Wt 41744.54.

Line 2 Ship Unit Count = 1, Total Wt = 1721.96.