you are already using a loop for printing the table rows, just use it to count up a variable which would be the row number, for instance:
$counter = 0; // initialize counter variable
while(... retrieving data record ...)
{
$counter++; // this increments the counter by one in each loop
// and now, you just print your table row <tr>...</tr>, including $counter in the "position" column:
...
echo "<td>$counter</td>";
...
}
I hope that's it!