Normally, Copy/Calculate fields are not evaluated in QUERY mode. This prevents the field from becoming part of the QUERY specification (unless the operator enters something into the field).
In some cases, however, you may want Copy/Calculate fields to be evaluated in Query mode. For example, your form has an invisible field that is in the data file and is calculated from an entry field that is not in the data file. If you want the operator to be able to enter a value in the entry field in QUERY mode and then FIND records that match the calculated value in the invisible field, you must set Do Copy/Calculate in QUERY mode to yes.