SAP Note 14068 - Log: Error when converting into other quantity unit

Symptom:

The message 'Error when converting into other quantity units' (message C7023) is written into the scheduling log when none of the standard values has a unit of time as its unit of measure.

Cause and prerequisites

During scheduling the operation duration is calculated using a formula
in a unit of time, that can be derived from the units of time of the
standard values.

Solution
At least one standard values must have a time unit.
Note: When calculating the duration using the formula, the system
first converts all standard values into the corresponding
SI unit. This value is then put into the formula. The result
is interpreted as a value in seconds which is then converted
into the time unit of the result.

Key word: Scheduling