What does 8CM and 12CM mean?

Question

I recently bought a Toshiba upconversion DVD recorder and I got 81 minutes on the XP mode which shocked me. But ever since that first recording I can only get a 63 min recording in the XP mode and sometimes 67 minutes. I've checked the owner's manual for answers to this and it says for 12cm disc you get 60 min in the XP mode but 121 in 8cm mode. I am very confused by this because there's no option on the recorder nor can I get it back to recording another 81 minutes in the XP mode. Was this a fluke or am I doing something wrong? My thanks in advance.

Answer 1

its the size of the disk, i think

Answer 2

Most dvd recorders have a button on the remote that will let u choose the record speed.  It is also inside choice of menu when setting a future show to record.