In Exploratory, you can create a survival curve using the Kaplan-Meier method. Typically, the survival time should start from zero when creating a survival curve, but in some cases, it may start from a negative value.
This occurs because there are rows in the data where the end time is set earlier than the start time, resulting in a negative survival time for those observations.
Please refer to the following for details and how to identify the data with such inconsistencies.