Questions involving the Type column of the Transactions table

Content

I have a column to track incidents created for live chat:

sum(if(transactions.trans_type=2&transactions.source_lvl2=1017,1))

We have the incidents set to be created automatically at the beginning of each chat.  The issue I have is the totals from the expression above do not match the chats completed:

chat_agent_sessions.chats_completed

It may be an assumption on my part that the first expression above only tracks incidents created for live chat (as the table description states it uses information in the audit logs for incidents and not chats), but am I wrong?  Does it also track chats that were created and not accepted?  Again, I'm just trying to figure why the first expression does not equal the second expression.