The Great Vault is displaying the wrong item level of next week’s rewards currently on live servers.
In Season 4, Great Vault raid rewards will pull from all Fated bosses you’ve defeated across the entire season, regardless of which raid is currently Fated.
Players who progressed through Fated Castle Nathria this week are reporting a visual bug where next week’s rewards show an incorrect Season 3 item level. The bug is likely just a tooltip oversight that will soon be addressed.
Source: Reddit