Conversion to the unit of measure chosen would result in an overflow

What causes this issue?

For one of the stock quantities, conversion to the unit of measure
chosen would result in a value that cannot be displayed in the stock
list due to its size.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Please choose an alternative unit of measure with a smaller conversion
factor so that the new stock value can still be displayed.

Error message extract from SAP system. Copyright SAP SE.