In principle the 2 standards are very similar, and the classifications are based on the same concentration of particulate. However there are a number of potential differences. I would recommend getting a copy of ISO14644-2015 Parts 1 and 2, and comparing them to what you do today. In particular, check out the required number of sampling locations and how the particulate numbers are used to obtain the classification. You may also have issues with your particulate counter meeting the ISO21501-4 standard.
One other point, make sure the information you use is based on the 2015 version of ISO14644. A lot of the information I see on the internet comes from the 2000 version which has a lot of differences, especially in sampling.