All pipelines seem to start with a non-zero duration however once the pipeline finishes the duration is correct.
To be more precise when the pipeline starts the clone step has a non-zero duration. After the clone step finishes its duration is set to the correct value and the next step has this non-zero duration added to it. Once the complete pipeline is finished all values are correct and this offset is nowhere to be found.
The following screenshot is from a simple “Hello World” pipeline during its execution. I cannot post the final result (which has the correct build time) as discourse only allows me to upload a single file because my account is new.