I found the below info on murthy.com. It looks like corrections can be made on the approved LC...
Chat User : I have got my labor approved in RIR. I do not have an MS equivalent degree, but I do have 8 years of experience. Can my I-140 be approved?
Attorney Murthy : Depending on the USCIS service center, it may or may not be possible to use experience to equate to the MS degree where the term "or equivalent" is not defined on the LC application. However, when the LC was approved, if the initial applicant who filed the ETA 750 B form was not qualified for the position, then a good attorney may be able to go back to the U.S. Department of Labor and request a correction of the job requirements on the grounds that the original applicant her/himself would not qualify for the LC approval. !However, when the LC was approved, if the initial applicant who filed the ETA 750 B form was not qualified for the position, then a good attorney may be able to go back to the U.S. Department of Labor and request a correction of the job requirements on the grounds that the original applicant her/himself would not qualify for the LC approval. Such corrections are difficult to obtain, but we have been successful with many such cases all over the country since obviously the attorney made a mistake when filing the LC as the person would not qualify for her/his own job