Based on the datasheet @Devaa provided, I would say there's almost a 100% guarantee that 50 Mbps can be provided, and a very good chance up to 250 Mbps might be provided (both license dependent). Whenever you get into boost license ranges, "your mileage may vary".
As M02@rt37 correctly notes, there's much that goes into achieving a bandwidth capacity, especially with crypto, but up to 50 Mbps, all those factors shouldn't matter beyond what exactly is considered the 50 Mbps, both for licensing and however you measure throughput. For example, I suspect you know a 100 Mbps link doesn't provide 100 Mbps (our) data throughput, due to L2/L3/L4 overhead, which, as a percentage, varies based on frame/packet size. Keep in mind, encryption may add its own (possibly considerable) overhead.
