On all trips with a calculated driving route, you will see an estimated time with stops and one without stops
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For the trip, under Edit → Trip info/waypoints, under the Settings tab, there is a section for "Time Calculation" that includes "Administration time per cache (seconds)". This is a fixed overhead that is added to each cache stop time to reflect things like getting in/out of car, doing paperwork for the find, figuring out where to go next, etc. The default value is derived from the corresponding setting in your personal settings.
Decide how much is appropriate for the trip. For example, a power trail with multiple people doing the running, signing and driving may have near zero overhead because it is overlapped with driving to the next cache.
If you have a hiking or biking trail with significant elevation changes, you may wish to take the elevation into account in the Time Calculation. For the trip, under Edit → Trip info/waypoints, under the Settings tab, there is a setting, "Extra time for elevation gain (seconds)". This value is used to calculate extra time for elevation gain specified in seconds per meter elevation gain. Values in the range 6-9 are suggested but you should decide what is good for you.