flow visualization - automatic scaling - what it means to set length > 1 ?

Hi! I read here : https://www.vapor.ucar.edu/docs/vapor-gui-general-guide/streamlines-stea... that the length variable controls "the number of crossings of the data domain of a flow line before the integration is stopped". And I am wondering what that actually means for a flow line. Does it means that if a line meets a boundary, it is going to stop when length=1 ? And when length=2 for example, it will stop integrating when the line meets the boundaries twice? Thanks! Lily