random chars in dynamic char array C

I need help with char array. I want to create a n-lenght array and initialize its values, but after malloc() function the array is longer then n*sizeof(char), and the content of array isnt only chars which I assign... In array is few random chars and I dont know how to solve that... I need that part of code for one project for exam in school, and I have to finish by Sunday... Please help :P

#include<stdlib.h>
#include<stdio.h>

int main(){

    char *text;

    int n = 10;

    int i;

    if((text = (char*) malloc((n)*sizeof(char))) == NULL){
        fprintf(stderr, "allocation error");
    }

    for(i = 0; i < n; i++){
        //tekst[i] = 'A';
        strcat(text,"A");
    }

    int test = strlen(text);
    printf("\n%d\n", test);

    puts(text);
    free(text);

    return 0;
}