If you read the consumption values on page 21 the cottons is 3 hours and 40 minutes as you rightly say the machine is adjusting the prog time according to soiling etc.
Virtually all machines these days have some form of fuzzy logic, smart wash, sixth sense or another name attached to their appliance.
If your items are lightly soiled why not look at the superquick options?
You need to have the instructions and sit in front of the machine with page 20 and have a play to familiarise yourself.
Don