Gold entity "Number"

Hi,

We have noticed, that the gold entity "Number" does not recognize one-digit-numbers (0-9) in a created intent.
Example:
"10 piece" --> 10 is recognized as Gold Entity "Number"; "piece" is recognized as custom entity

"1 piece" --> "1 piece" is recognized as custom entity
--> this is wrong; it should be: 1 is recognized as Gold Entity "Number"; "piece" is recognized as custom entity

Does anyone know how to solve this issue? Is the gold entity not trained correctly?

Note: Example is in English; we are using it in German.

Thanks & BR
Simon