Yes you are right, the build number for April 2017 CU is
But I advise you to don't trust the build number in Manage Servers in Farm, it often gives you a wrong indication about installed fixes.
Stefan Goßner discussed the reason in details at SharePoint patching demystified I quoted some
One reason might be that you looked at the KB article for SharePoint
server and not the one for SharePoint Foundation. These two components
might have slightly different version number – e.g. the SharePoint
server package might have been created a couple of days later than the
SharePoint Foundation package. As the version number on the "Manager
Servers in this farm" page in the Central Admin only shows details for
the SharePoint Foundation component you cannot expect to see the
version number listed in the SharePoint server KB article.
But even when looking at the SharePoint Foundation KB article there
are rare cases that the patch level listed in the central
administration is lower than the version number in the KB article. The
reason for this is that different fixes are added to the CU at
different times. Some fixes modify DLLs of the components other just
Microsoft.SharePoint.dll as this is the core component of the
SharePoint Foundation component – so its version number usually has
the highest version number in the package. But not always! It might be
that the last fix being added to the package is a different file. If
this is the case, then the version number in the KB article might
reflect the version of this other file. If this file is a DLL you can
verify this in explorer. But if this file is just a CSS file or a
information then you might not be able to identify the file which
defines the version number in the KB article.
To check Get the Products and Patches build numbers that already installed on the farm.
Check the install status and version columns for all installed Products/Patches.
Also, check other alternative ways to Find Farm Patch Level/ build number