sscanf_ tricky func

I figured it out by trial.
But I dont understand how it works.

buff[8] , (sscanf(&buff[0], "%x", &x[i]) reads out the 1. row (x)
buff[9] , (sscanf(&buff[2], "%x", &x[i]) reads out the 2. row (y)

Code:

#include<windows.h>
#include<iostream.h>
#include<conio.h>
#include<stdio.h>

int main()
{

char buff[9] ;
int i;
int x[10];

FILE *Hex;
Hex = fopen("hex.txt","r");  //Liest von hex.txt

clrscr();
  while (i<10 && fgets( buff, sizeof(buff), Hex)!= NULL )
  {
    if (sscanf(&buff[2], "%x", &x[i])==1)
      {
       printf("sscanf=%d  i=%d %x\n",sscanf(buff, "%x", &x[i]) ,i,x[i]);
       i++;
      }
   }
getch();
}

How does buff size affect the outcome?

Show us the text file

There's no point making buff unnecessarily small
char buff[BUFSIZ];
is the usual default

> How does buff size affect the outcome?
Lines longer that sizeof(buff)-1 get split into multiple parts, which result in multiple calls to fgets, and more increments to i than you expect.