The 4th paragraph builds on the 2nd and 3rd paragraphs, providing further details about the claims. The 4th paragraph states that a claim in dependent form must make reference to a previously stated claim and specify a further limitation. In other words, the 4th paragraph indicates that you can't just keep repeating the same claims; each must add some substance to the application or they should be left out. The 4th paragraph goes on to say that by their nature, dependent claims always incorporate by reference all the limitations of the claims they refer to.  

And here's what is meant by this. If the initial claim states your new battery recharger operates between 100 and 300 amps, then a subsequent dependent claim may not broaden that figure into something else (for example, between 10-300 amps). It's common sense that a dependent claim cannot be broader than the claim from which it depends.