This tool compares a selected player's performance over a defined span of seasons to similar players who signed contract extensions immediately afterward. Based on those comparisons, it projects the expected extension value of said player if they were to be an upcoming free agent. Selecting 2024 as the start year gives you a larger basis of comparison but a smaller sample for the player, while selecting 2021 gives you a smaller basis of comparison but a larger sample size for the player.
I recommend selecting 2023 as the start year to get a multi-year evaluation period.
Select a position and year range, then pick a player to see contract projections.