Postgrad Masters Loan

I am taking a Masters course in September, but when reading the Masters Loan on GOV UK, it isn't clear whether you can specify what amount you need. It says up to £12,000+ but I won't need that full amount. For anyone that knows or has had one before, am I able to specify an amount that I need from that £12,000+? May seem like a silly question but the wording isn't 100% clear and just want to know all my options!
Thank you!