There are a number of ways of delaying the start of the logging.
The best option is the “Specify delay date and time”. This allows you to enter a specific date and time at which the unit will start.
The specify start duration provides a simple method to just use a fixed delay (e.g. 1 day) but people tend to prefer the specific date/time option.
In some models it is possible to start logging once the unit goes into alarm (that is it goes below the low limit or above the high limit). This is handy when monitoring events that are outside normal room temperature. For example, setting the low alarm to 10° will then cause the unit to start logging once it is placed within a fridge. Of course it assumes that normally temperatures won’t fall below 10°. Possibly not ideal in winter.
But most people just go with an immediate start and don’t worry about delaying the start.