How long should the “frosting” look last on cafe au lait macule when immediately treated by Picosure (755nm)?

I had a second treatment of Picosure for a cafe au lait macule on my face. The end point of the procedure, particularly the “frosting” look was present for less than a minute. Is this normal? Also, the doctor only did one pass on the CALM. I’m hesitant to return to this place since my birthmark did not respond to the first treatment of Picosure. How long does the “frosting” supposedly last? Is this a tell-tale sign that the treatment will be effective?