Hi Rob,
It looks like the Grandstream is sending 3000 in as a DiD to SAIL. Up until very recently, SAIL would not accept a 4-digit DiD so you have to get the grandstream to send a longer digit stream. As an example, you might have it send the full external number of the line (all 10 or 11 digits, depending upon your national PSTN). You would then create a PTT-DiD-Group with the full number and, in turn point the PTT_DiD trunk at the extension you want to hit (in the OPEN or CLOSED inbound route). Which looks like what you've tried to do, but I think you've sent the number in as 3000 instead of 5074731143.
However, in -670 (which is very new), we changed the rules so that you can create a 4-digit PTT_DiD. You can also use something called "smartlink" which will look to see if there is an extension which matches the last four digits of the DiD and, if there is, automatically fill out the routing for you. So if your Grandstream is sending 3000, then simply upgrade to 670 and create a DiD for 3000. SAIL will automatically point it at exten 3000 (as long as you check the smartlink box in PTT_DiD create panel) and you should be good to go.
Hope that this helps
Kind Regards
S