@Souvik30 

Hi, which firmware page are you talking about? You can find the firmware page from below link:

https://www.tp-link.com/support/download/archer-c6/#Firmware

Archer C6 v3 does not support bandwidth control (limit bandwidth per device), it only supports QoS. You can refer to the below instructions to get the configuration guidance:
https://www.tp-link.com/support/faq/2797/

We have feedback to the related department, and the bandwidth control feature will be available on the wireless routers in the future firmware update, but we cannot provide you an ETA, we cannot know which model will have it at the moment.

You are suggested to pay attention to the official website, or the new firmware notifications on your router web GUI for any new firmware updates.

If this functionality has determined the choice of equipment, you can return the router to the place of purchase as not as described.

@Souvik30 

Got you. The local website will be updated soon.