Everybody have 3 plots, the 3/2 plots is just a bug, so you can have a 3rd plot do not worry :D (You can have more plot if you have a higher rank, or Mapper (25 plots for mapper))
How to merge a plot: (Have two claimed plots together, also have the merge tool bought in the mana store! (/shop) Face toward the other claimed plot while standing on the other claimed plot) /plot merge
How to merge a plot: (Have two claimed plots together, also have the merge tool bought in the mana store! (/shop) Face toward the other claimed plot while standing on the other claimed plot) /plot merge