1. The change - is your type of income and manner of taxation changed. Perhaps you sold long term stock.
2. The difference - Let's start with Form 1040 Tax Tables (2024) which contains the answer.
Box 1 tax table -is the actual tax tables found in the link
Box 2 tax computation worksheet: Instructions for Form 1040 Tax Tables (2024) states:
Note. If you are required to use this worksheet to figure the tax on an amount from another form or worksheet, such as the Qualified Dividends and Capital Gain Tax Worksheet, the Schedule D Tax Worksheet, Schedule J, Form 8615, or the Foreign Earned Income Tax Worksheet, enter the amount from that form or worksheet in column (a) of the row that applies to the amount you are looking up. Enter the result on the appropriate line of the form or worksheet that you are completing.