Upgrading Jira Core 8.2.3 - 8.17.0

[IT]

Hi there, 

Upgrading the package form 8.2.3 to "Whatever" this seems to have 2 packages the software component and core component.

The wizard allows the upgrade of 8.2.3 - to - 8.17.0 of the software package but NOT of of the core package... and jeezus but do Atlassian know the manning of Matrix? is it just me or is there no listing of upgrade path for compatible versions? The link that supposed to have the matrix but its a listing of features for each of the versions.

Can I keep the Core Version at 8.2.3?... if so for how long?
What version can I upgrade core to? and is there other versions steps.

Marsbar