At which time subscriber should sample the packet for coverage?

Let me to add more information, I am not having different transactions for master and slave side, both monitors are sampling AHB based write operation as well as read operation from interface and sending to scoreboard and subscriber.

Eventually both monitors sampling the same data and sending to subscriber and scoreboard. Practically thinking, only one of the packet is needed to sample which will generate coverage but if there are some errors in one of the monitor and if its packet is not getting sampled then coverage can’t be considered perfect. So in this approach, both packets are needed to be sample.

So my real question is, do we need to sample only one packet of both then which one, and if both packet need to be sampled then how to avoid double sampling?