PSC PowerScan LR Handheld "15cm" Questions

I have a PSC 959 wireless barcode scanner and it does not work at the indicated distance from the barcode (15cm). What can i do to fix this? Scan the code on the base station

distance capture code MC9090 Hello need help set the distance of reading in my power to you collector mc9090 You must be at distance of 15cm in a angle of 90? to capture de reflesh of the ticket.