Update to 5.2.6?

As a new user, I’m happy to be out of MS Office.
I’m having confusion about Updating.
In an open document, upper right corner, there is an update button. When I click on it, this message appears:

LibreOffice 5.2.6 is available.
The installed version is LibreOffice

Do I need to uninstall
I’ve tried clicking on the update button, then my Dell laptop takes 40 mins to dl approximately 256MB.
Is this a dl of the entire suite?
Shouldn’t the updated files be those that are dl’ed?
Thanks for any help.

The downloaded file is the main LO installer. There’s no differential updater (yet) for LO on Windows (assuming you’re on Windows, of course; you didn’t tell that).

The updater will correctly detect and uninstall previous version itself, so you don’t need to uninstall it first. Moreover, if you uninstall it first, then you will need to manually select components of your choice on installation, something that is handled automatically on upgrading over existing installation (when it updates all installed components).