To correctly use of conditional and default sequence flows, keep in mind that ‘conditional sequence flows’ are only used in certain situation and there may be only one ‘default sequence flow’ per object.
Conditional flows are sequence flows that take precedence under certain conditions. The default flow stands for the ordinary sequence flow that has to be followed if neither condition is met. The conditional flow is followed only in special circumstances. The conditional flow needs to have a label that describes its condition, for instance ‘invoice amount 5000€’ so its clear when to take this path in the process. Generally, only one ‘default sequence flow’ is allowed per element.