TexasCHLforum.com

These all sound like small population counties. That would mean that the high percentages could represent a small number of people. To test that theory, I looked at Brook County.

Population 7,237 in 2013 and the trend is a declining population (In 1984 the population was 8,797.)
According to the Texas Secretary of State website, in 2014 Brooks County had:
Registered Voters 6,433 Actual Voters 2,146, Percent Voting 33.36%, Early Voters 1,314, Percent Early Voting 20.43%

So, not only do they not have more registered voters than the total population (or are they referring to voting age persons??), only 1/3rd of those registered actually voted.

Let's look at another county - Jim Hogg County
Population 5,245 in 2013 and the trend is stable (1984 the population was 5385)
Registered Voters 3,853, Actual Voters 720, Percent Voting 18.69%, Early Voters 332, Percent Early Voting 8.62%

It doesn't look to me like there's a problem in these counties. I wonder where they're getting their numbers from.

I'd be a lot more concerned about a large county, such as Dallas County, having over-registration, then small rural counties with very low populations.