We have two fresh Zabbix installations - one on a master node and the other on a slave node. Thus, there are two hosts linked to Template_Linux.
See all-nodes.png. This is the status of Zabbix when "All" nodes are selected. The number of monitored hosts (2) is the sum of the number of hosts for all nodes. The number of users (4) is also the sum of the number of users for all nodes.
See master-node.png and slave-node.png (they are identical). These refer to the situation where only one node, master or slave, is selected. The number of monitored hosts is still shown as 2 (the sum), but the number of users has changed to 2 - the number of users on a single node.
PS: Note in all-nodes.png that under "System status" the order of nodes is "Node at 192.168.3.4", then "Node at localhost", but under "Host status" the order of nodes is reversed.