It's noted in the data sheet as Concurrent IPsec sessions. Each VIA client will consume one IPsec session or SSL session.
So, for the 7005 it's 1024.
Please not that this are combined numbers.
Each RAP/VIA client will consume 1 IPsec session
But a VIA client will also count as a user in the user-table. The total limit of users in the user-table is 1024 for the 7005.