Click "Advanced Options" tab in the dialog, you can set advanced options in recovery process.
•"Directory for temporary files"
DOEDR uses this directory to create temporary files. By default, this field is set to Windows temporary directory. If it is blank all temporary files and folders will be created in the current directory.
•"Internal Processing Buffer Size"
You can set the size(in bytes) of the buffer used for internal processing. Valid buffer size ranges from 1 to 32767. And the default value is 512.
If the file where the deleted emails are to be recovered is located on a reliable media, such as a hard disk, then you can set buffer size to 32767 to obtain the maximum recovery speed. However, in most cases, the performance of the default value 512 is similar to that of 32767.
If the file is located on a corrupted media, such as a damaged floppy disk, then by setting a smaller buffer size, you can force DOEDR to perform a more thorough scan and recovery. In an extreme case with buffer size equals to 1, DOEDR will perform the most thorough scan but this will reduce the speed dramatically and is only recommended for relatively small files(1MB to 10MB).
In a word, by increasing the buffer size, the recovery speed is increased but the thoroughness will be decreased if your file is located on a corrupted media. And vice versa.