Hi,
The maximum number of concurrent sessions varies depending on what each user is doing and the number of Bastion instances. For example, for "medium" workload each instance can support 20 concurrent RDP and 40 concurrent SSH sessions. For Azure Bastion Basic SKU, you are limited to 2 instances, whereas with Standard SKU you can have up to 50 instances.
If each user is performing tasks that involve lots of data transfer then less sessions per Bastion instance will be supported.
Instances and host scaling
https://learn.microsoft.com/en-us/azure/bastion/configuration-settings#instance
Azure Bastion limits
Please click Accept Answer if the above was helpful.
Thanks.
-TP