If you’re referring to the number of errors that can show up in red on the Settings page under Chart and Data Synchronization, then you should be able to tap Update Now to have Coastal Explorer retry the parts of the chart that failed to download. That will only try to download new data and data that failed to download previously, not all of the data.
But you might need to adjust your download area first if you aren’t getting the charts that you want. We just added an article that might clear some things up for you. See Using Coastal Explorer on your iPad or iPhone Without the Internet.