It does not make it clear, but it seems this device does not come with any memory itself, so you will have to BUY some memory before you can record anything.
This memory would be an SD card (like used in camera) or a USB stick.
You would need to buy a decent amount of memory to make it worthwhile (at least 8Gb) which would set you back at least £10 more.
Once you use up that memory (only 8 hours worth of TV) you need to buy more memory.
I would say DONT buy it.
Far better to get a freeview box with a hard disk in it, often called a PVR.