A warning of strange meaning

I have seen this warning a few times when I compile this line of code, the warning is this:

warning C4267: '=' : conversion from 'size_t' to 'int', possible loss of data

The code is this:

Code:

---

char senta[]="I am an example!"

            size=strlen(senta);
            for(x=0;x<size;x++)
            { 
                Sleep(40);
                printf("%c",senta[x]);
            }

---

Sorry if the indents a little rubbish, but the warning it produces does not change my output.. what does it mean? I have looked
in my compiler log and can't find the answer...

size is (presumably) declared as type int and strlen is returning a value of type size_t.
You can remove this warning by declaring size as size_t

Code:

---

size_t size;

---