Multiline sip phone setup best practice

Hi, I am deploying freepbx with about 25 Aastra 9480i desktop phones. These are multiline phones and the web interface to them has a “Global Sip settings” as well as settings for individual lines. (e.g. Line1, Line2, Line3, etc). Currently, I have the receptionist desk phone configured to use the same extension on all four lines (i filled in each screen for line1, line2,…) after trying to use the Global SIP settings which failed. For all other phones in the office should I put the individual users extension on Line1 and the receptionist extension on the others -Line2,Line3,Line4? Or should I configure all four lines on each phone to be that of the individual user extension?
thanks for any pointers as I am new to multiline phone configuration.

If anyone has pointers, please share. Thanks much.