Diamond: Warning: logical net has no load
This is a pet peeve of mine with synthesis tools in general &mdash; they tend to spew out a lot of irrelevant warning messages that make it very difficult to find the real errors in a design.

In this case, it seems that the tool has recognized that your countdown variable is a counter, and used a general-purpose counter macro to implement it. However, this general-purpose macro has outputs that you don't need &mdash; and have no reason to know about in the first place. But the DRC cheerfully puts out warnings related to those outputs that mean nothing in the context of your actual design.

Short answer: These particular warnings are safe to ignore, but you can't generalize from that.