I have a question about the mining.set_difficult method.

In the example here https://mining.bitcoin.cz/help/#!/manual/stratum-protocol

the first time the parameter here is a string (I would say it's the target), but the second time its a number.
Is it supposed to be a string only if it's a result to mining.subscribe or should the client handle both?

Another question is about the result to mining.subscribe. Can the result have an arbitrary number of [method, params] pairs or am I missing it completely?