/1/ do I want to back up Folder or File?
If you select "File", then only one selected file will backup. Selecting folder will backup the contents of the entire directory and all sub-directories.
/2/ do I have the incremental box checked?
If you check "Incremental" backup, then only files in the source that changed from the last backup will copy from the source to the destination. Additionally, files that were deleted from the source will remain in the destination, so over time the backup copy will grow larger and larger than the source.
If "Incremental" is unchecked, then a complete backup of all selected files/directories will copy with each run and will overwrite the files/directories in the backup location.
Unchecking "Incremental" can kill your HDD if you are running frequent backups of large volumes of data. I use a hybrid approach: (1) perform nightly incremental backups; (2) Schedule a weekly run of a third party backup application from a PC that deletes the files in the destination that are not in the source. This approach keeps the source and destination in sync without transferring large volumes of data.