They say it's 100% of the full-time salary, but the one open position they have is a full-stack JS engineer for the equivalent of about $66k USD. Is the market really that bad in the UK? That's not even a good new grad offer in the US.
You can't directly compare salaries with the US though : the tax and benefits structure is vastly different.
Better in my experience : https://www.itjobswatch.co.uk/