My SD card is a nominal 64 GB (actual 59.6 GB)
Currently showing only 3 GB free/ 56 GB used
The maps folder is 12 GB
The Android/data/com.avenza/files folder is 24 GB
The rest is basically zero (a few MB).
So what happened to the other 30 GB? – This looks like a generic SD card partition issue.
I think I need to create a new 30 GB partition on the SD card but in order to do this without risking my 232,795 files in 686 folders (actually 803 maps in 61 folders) I will make a backup first.
I will let you know how it goes.