Hi @chrisyan
For read audience journeys you only get the reentrance option for recurring journeys. The journey shown i screen shot you shared is for non-recurring/“one-shot” journey (i.e. "Scheduler Type" = "As soon as possible").
To get the reentrance option for this journey you need to change the scheduler type to either daily, weekly or monthly. Once that is done you'll get reentrance options as below,

You can follow profile entrance management documentation for more details on reentrance for different kinds of journeys.
Cheers!