Thats a bit rubbish isn't it
I didn't believe you so I tried - you're right, you can't type "19" into the box - write that one down to a web site designer geek falling asleep at his mouse the day he did the order form
Ring the shop at 0844 248 6651 and do your order over the phone, then tell them why you couldn't order online, they'll be wondering why no-one likes the number 10 upwards