I've not had an issue with the same extensions being in 500 and 506.
500 is the "goto operator" in the SVMi-20e EClass and MClass settings.
506 is the "Press [1] for recruiting" from the menu system.

The guy who set this up originally had all extensions (When the company was small) in both 500 and 506. (There were less than 32 extensions back then.)

Things are working ok so far. I'll test the GPIK buttons after hours on my phone.

I created a beast when I showed them I setup an SMDR to SQL capture program for call accounting and wrote a few reports.

My next job is changing the main greeting prompts for day, night, holiday and inclement weather and reworking the menu. "Please listen carefully as our menu options have changed..."

Thanks for all of your insight and help!

"Try not to become a man of success, but rather try to become a man of value" ~ Albert Einstein