Split-044 (or variations) just means what it says: It was just split from a larger whole

and it auto numbered. Usually folk split at chapter heading (aka start of chapter) so no Anchors (<a id=) to land at are needed.
Calibre has 2 places for TOC editing:
1) Is in the editor. 2)can be added to the toolbar.
Blue just is the standard (and default) for
This is a a Link.
Code:
<a href="../Text/bk1.htm#chapter_1">BOOK ONE</a>
(the #xxxx part just indicates that the target is at a specific marked location in the target file)
Blue only is visible on color screens and personally, I don't use inline TOC as my devices all have a TOC jump on the menu (the book current reading location remains unchanged unless I select a a new location from the TOC)