The Licence Protector MAC Edition Serial Number is always in the following format
ldGEl-5IPc3-9E8Iq-3tQ8X-PQU5k-6m14D
There are situations, especially with CD distribution, where a short number with only upper case letters would be ideal. If you create your own Serial Numbers / IDs you have to just ensure, that they are unique.
To ensure, that only IDs are accepted, which belong to this product, you have to upload the IDs to the Activation Server 4 and you have to configure the project, that only uploaded IDs are accepted.
See chapter: Accept only uploaded Serial Numbers.