Was Sent: [this email asset] between this date range min number of times: 2
will function as
Was Sent: [this email asset]
between this date range
min number of times: 2
When you have multiple values inside a single constraint, that is "or" logic.
Was Sent: [this email asset OR that email asset]
There is not a way to change the logic of constraints, so if you wish to have some sort of 'Or' between constraints then you would have to use multiple filters with 'OR logic between them.