Ring Round - configuration

Hi there chaps.
I’m sorry but I’m relatively new to programming asterisk and have been amending what I have been left with when deploying new extensions etc.
I currently have an issue with the ring round part of the configuration in that extensions in the 613 part ring even though the call may have already been answered and when answered the line is naturally dead. I would like to know the syntax / variables / switches of the following and also if anyone can spot any obvious glaring problems. Also if I ring 613 the group of extensions ring but the line signals unobtainable. Thank you in advance and please do point me in the direction of any appropriate documentation/posts.

;incoming calls dial ext 601. This rings round using the following line


;group of Reception1, Reception2

;group of Ext 205, Ext 207, Ext 209

;group of Ext 305, Ext 303, Ext 302

;group of Ext 204, Ext 301, Ext 304