Issues with Symetrical bandwidth

Hi there, could anyone lend advice on how we are able to get symetrical bandwidth working? Our customers are reporting slow upload speeds. For instance, customers get the full 1024 down and only 350 up. Any help would be appreciated.

Set the percentage to 50% up/down. However, that will result in lower speeds down. By the sounds of it, the units are being set to a lower throughput anyway.