A couple of issues on data-driven subscription on a local computer with multiple SQL Server instances

1. I used a named SQL Server 2012 instance (which is called SQL2012) for the Subscriber database. The SQL Server agent for this named instance already started. But I keep getting an error message complaining the SQL Server Agent is not started. After I start the SQL Server Agent for the default instance, which is for SQL Server 2008R2, the error message is gone and the subscription is saved. Why so? because I specify http://localhost/reportserver for the TargetServerURL on the project property. If I specify http://localhost/reports_SQL2012 as the TargetServerURL, I would not need to start the SQL Server Agent for the default instance.

2. I used my laptop for the project and created a shared local folder called Tutorial at C:\Users\CK\Documents\Tutorial. After I use a correct UPC as either \\localhost\Users\CK\Documents\Tutorial, or \\MyPCName\Users\CK\Documents\Tutorial, I have four files instantly populated in the 'Tutorial' folder. However, the message under the 'Status' tab on the My Subscriptions web page in report manger is "Processing: 0 processed of 4 total; 0 errors.". It takes about 10 minutes to change to: "Done: 4 processed of 4 total; 4 errors." 

a. Why so long? 
b. Why 4 errors? 
c. Where are the errors?

I have checked the event viewer and the tables ExecutionLog, ExecutionLog2, ExecutionLog3, or ExecutionLogStorage in the reportserver database. All reported a status of rsSuccess with the correct numbers of row counts. These may be just some of the minor bugs in SSRS.