What does the data look like in this field?
If you have
in a field named "Value", then Length ( Value ) will return 2, that there are two characters in the field.
in the field, length will return 4.
But if you also have spaces or other characters in the same field, you can see 4 visible characters but length will count both the visible and invisible characters in the field.
You might need to use:
Length ( Filter ( Value ; 9876543210 ) )
to get a count of just the numeric characters in the field.