Specific:

%2d: Output data in 2-bit format. If there are less than 2 digits, fill them with spaces to make up 2 digits; If it exceeds 2 digits, all digits will be displayed. For example, if you want to output the number 2, the output result is "_2", "stands for space; If you want to output the number 1234, the input result is "1234".

%02d: If you understand the above format, you will understand it better. 0 means less than 2 digits, so it should be filled with 0, not the space above. For example, if you enter the number 1, the output will be "0 1". If it exceeds 2 digits, all digits will be displayed, and 0 will not be filled.