Calculating delay for Toggling LED to visually check for data transmission

I am transmitting data to another board and use LED toggling to verify the data transmission. Since I need to visibly make sure that the data is tranmsitted, I have to give a certain delay (bsically a simple while/for loop). I have come across function with a value for the loop. I need to know the basis for that value in the loop.

For example ,

    for(i=0U;i<10U;i++)
    {
    }/* Wait */

 How to decide a value of XXXX to select a 4ms delay????

Also how do I decide a delay of 4ms in my TI-Hercules TMS570LS3137. Could anyone please explain.?