I got it:

Here's the code to copy:
CountIf(Split(TEXT_FIELD, ""), Len(Value(ThisRecord.Value)) > 0)
Here's what it does:
1. The TEXT_FIELD that you want to search for numbers is split by each character
2. Each record's value (in this case, every character) is converted into a number
a. If it's already a number, this will return the character
b. If it's any character other than a number, it will be a blank record
3. The length of each character as a value is checked. If it's a number, this will return a 1. If it was another character that is now a blank record, this will return a 0.
4. Every 1 in this list is counted, returning you the number of numbers in your text field
My explanation might be a little confusing, but if you plug in the Split code into a list box it will help it make sense.