Some nodes in KEGG pathways may represent multiple entities. For example, different isoforms of the protein, subunits of proteins, members of the same gene family, etc. . All entities under the node get selected when you select the node on the pathways.
Mouse over the node of interest to view all the entities under the node in the tooltip. You can also select the node to filter the heatmap below to limit it to only the entities represented by the node. Specific entities under the node can then be selected from the heatmap.