Tree Conflict Issues

Using Tortoise 1.6.6.17493. Repository is version 1.6.

I'm trying to educate myself (and my team) on resolving merge conflicts. However, I'm really not understanding certain tree conflict errors that often pop up.

Here's an example (see attached screenshots for reference). Yesterday, I made a branch from the trunk in a project, made a bunch of changes, and am now attempting a "Reintegrate Branch" operation.

No modifications have been made to the trunk since I made the branch, and I did not touch these 4 files in my branch. If you look at the log for these files in the branch, the first line shows that I copied it to my branch, and the second line shows the current trunk revision.

So, first, I'd like to understand why this tree conflict exists?

My other questions the conflict resolution dialog itself (see attached):

1) Where did the revision numbers 5951 and 6012 come from in the "Source left" and "Source right" fields? 6012 is higher than any revision in the repository, as far as I can tell, and 5951 is way less than the current trunk.

2) There is a "show log" button there...but what is it showing the log of? The trunk? The branch? A combination of both?

3) How come I can't VIEW and/or compare both revisions? It's very hard for me to decide which file to keep when I have no idea the contents. I can go to my local copy to view the "local file", but I'd like to be able to see the repository version too.

Thanks in advance for any help you can offer.