This seems clear to me? (from Page 2)
Direct dialled call charges
Call charges are shown in pence per minute but you will be charged for the time you are connected to the network.
Call durations are accurate to plus or minus 1.1 seconds and rounded up to the next minute.
Charge band periods are accurate to within plus or minus one minute.
Call charges are rounded up to the next penny. A call connection charge of 11.99p per call applies unless otherwise stated.