Interactive YouTube video navigation
You'll need to make a separate spotlight for each different link.  So one spotlight goes from 5 seconds to 6 seconds, and another spotlight goes from 6 seconds to 7 seconds.  Each of them starts your linked video at a different point (15 seconds, 16 seconds, or whatever).

It's easy to set the starting time within an annotation link.  When you create the annotation, and add the link URL, it will ask you about the starting point.  (The default is 0.00, the beginning of the video.) You just set it there before you publish your annotations.

Note that annotations don't yet work on mobile devices (as far as I know).

Here's a useful page that instructs you how to create and use annotations, in case you need some more info.