Hello!
The "%i" in you code is the format specifier that determines the output format in which "fscanf" will write the data that is stored in the variable 'i'.
For example, in your case, "%i" refers to a Base 10 Signed Integer format, and the data in variable 'i' will be written by function 'fscanf' in that way. Similarly, "%u" represents Base 10 Unsigned Integer format, and so on.
The exhaustive list of all format specifiers used by the function "fscanf" can be found in its documentation page at this link:
Hope this helps!