MA create new folder in my SD card and restarted photo name counter from 0001 after the original folder file name hit 0999. As the file name counter has 4 digits can we set the folder full when the counter hit 9999?

It's a small joke from Dji.
https://forum.dji.com/thread-124014-1-1.html

DJI does not follow the standard to its full extent.

4.3.1   DCF file names
File names conforming to the following rules are called DCF file names.
• The file name is 8 characters (not including the file extension).
• The first four characters consist only of the upper-case alphanumeric characters shown in Table 1
• These are referred to as the DCF file name Free characters. They shall not contain two-byte characters or special codes.
• The four characters that follow are a number between "0001" and "9999". "0000" shall not be used.   These four digits are referred to as File number.
• Files with the same file number stored in the same DCF directory are considered to be object component files as defined in 4.3.2

Document link

This looks stupid and make me more difficult to file my photos. I took a lot of photos and very easy to get duplicatesd file.

DJI should fix this issue and increase camera system counter to 4 digits.

Hi, sorry for the inconvenience. Please refer to this thread: https://forum.dji.com/thread-124014-1-1.html, the largest number is 0999 and it doesn't support to change, please be noted.

The engineer should look to fix this.