Notification Limitation?

I'm wondering if there is a notification limitation in Quickbase.  Both searching Quickbase resources and performing google searches has not turned up anything, so hopefully a little guidance from someone who knows more than me can tell me where I'm missing a step: 

I have two tables in an app.  All Other Inventory is the Parent and Employee Records is the Child.

1.    Employee Records – in this table our Help Desk can assign to an employee an inventory item such as an apple pencil along with the qty.

2.    All Other Inventory – in this table I have every Inventory Item listed, along with how many I have of each.  If an employee is assigned 1 Apple Pencil, then the total number in inventory is decreased by 1.  If I remove the apple pencil from the employee, the total number in inventory is increased by 1.  The math works, no matter what the item is, so we're good up to this point.

The issue that I'm running into is with the Notification that I created called Apple Pencil Inventory Low.  Here's the criteria:

Notification when an inventory item is modified.
AND when
Number of Items Available (this a Formula – Numeric Field, [Total Number Of Items in Inventory]-[Number Of Items in Use])
AND when the following conditions are true after the change:
all conditions are true
*Inventory is equal to the value Apple Pencil
and Number of Items Available is less than the value 5

Then a Custom message is sent out to a recipient (myself in my testing).

*Inventory is a field in the All Other Inventory Table that lists each item we have in Inventory, such as a Apple Pencil, Apple Keyboard, Mouse, etc.

My question is, because the field Number of Items Available is a Formula – Numeric field, and not Numeric, is that the reason why the notification will not work?  If so, is there a way around this?

Thanks in advance!

Stu