Excel lets you put numbers into a formula, but this is rarely a good idea. To quote from the FAST standard:
“…Embedding commercial information, for example an inflation rate, is never a good idea, as both clarity of model assumptions and active parameterisation are lost.
However, not all embedded inputs are created equal. Embedding a 24 (for 24 hours per day), 12 (12 months a year), 1000 (dollars in $ 000s) is permissible, even sensible. “
Other standards and best practice guides take a similar approach.
Openbox therefore warns you about any formula that contains a number. You can choose to ignore the message.