they are cumulative - just install it in your Content Manager after you have downloaded it in the Marketplace.
MS is going to continue to update the regions as they get new satellite imagery and perform needed photogrammetry adjustments..untill their work on MSFS2024 gets in the way.
IMPORTANT - whenever you install Region Updates, or City Updates, you want to clear your Scenery Cache in MSFS - unless you don't cache scenery - before you fly in that area.
Otherwise you might see some issues that shouldn't be there.