Usually a community search should find multiple posts on this already.
I therefore updated the Skype for Business FAQ to contain this information already in the text and the post itself in addition to the Admin Guide outlines this clearly:
Jan 04, 2016Question: Can I change / re-assign the appearance of a Line and / or Presence Keys?
Resolution: Please check => here <= and the limit using EFLK is 100.
Please ensure to provide some feedback if this reply has helped you so other users can profit from your experience.
Polycom Global Services
---------------- The title Polycom Employee & Community Manager is a community setting and does not reflect my role. I am just a simple volunteer in the community like everybody else. All posts and words are my own & do not represent the views of Employer.
Notice: This community forum is not an official Poly support resource, thus responses from Poly employees, partners, and customers alike are best-effort in attempts to share learned knowledge. If you need immediate and/or official assistance please open a service ticket through your proper support channels. Please also ensure you always check the VoIP , Video Endpoint , Skype for Business , PSTN or RPM FAQ's