I am trying to understand below C program

#include <stdio.h>

//#pragma pack(1)

struct var1 {
    char data1;
    char arr1[10];
};

union var2 {
    int data2;
    char arr2[5];
};

int main(void){
    printf("var1: %lu, var2: %lun", sizeof(struct var1), sizeof(union var2));
    return 0;
}

The output of it

 gcc-12 -Wall struct-union.c

output

var1: 11, var2: 8

Why var1 is not 12 bytes?

environment

 Linux n 6.5.0-28-generic #29~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Thu Apr  4 14:39:20 UTC 2 x86_64 x86_64 x86_64 GNU/Linux