VMware ESX hosts are patched according to a model where each patch bundle only updates a few components of the ESX installation at a time. Not all components of the installation are upgraded
As a result, the ESX installation can have different components at different build numbers, depending upon which patch bundles have been applied.
If you wanna dig deep into the details of the build on your host.
check this KB.
VMware KB: Determining detailed build number information for VMware hosts