Since the maximum spool length for Digi-Spools varies by part number, and for now they don’t seem to be listed as an attribute on the website, it seems like a good idea to note some of them in the forum.
For part number 484-DR-25-TW-1-0-SP-DS-ND, the standard manufacturer spool is 30 meters, making it the maximum length that can be put on one Digi-Spool as well.