The Digi device and terminal servers which have MEI serial ports can support up to 32 slave devices as per the standard for RS-485 serial line drivers. If you have more slave devices than that you will need to add a repeater.
However, although the configuration allows for up to 255 individual protocol addresses, which would in theory allow up to 255 total slaves, practical considerations will limit your total number of slave devices. These limits are dependent on the number of masters, the polling interval, the specific configuration (whether there are serial radios or other additional communication technologies which could affect polling speed and response), and other factors.
May 15, 2019