it's hard to nail down without your filing status and other info how the income is made up (long term cap gains etc) but rough thoughts...
1) 23493.1 (Box 1b+2a) taxed at long term cap gain rates likely hitting 15% = $3523
2) 9325.1 (Box 1a - 1b) taxed at ordinary income rates not sure you filing status and bracket but if single it could be as much as 35% = $3264.
(see Qualified Dividends and Capital Gain Tax Worksheet for the calcs/tax table amounts for 1+2).
3) you're saying nothing else changed on 1040 but do you mean before Line 15; is there effect on tax reported by Schedule 2 / Form 8960 / 1040 Line 23 due to NIIT? This would 3.8% for some amount, possibly not all of the amount from this 1099 depending on threshold but Form 8960 would be adding in Box 1a + 2a (32819) with your other investment income in the threshold/calcs.
1+2 at least get to $6787 you had $6953 effect so it's a reasonable tax amount from what I can see, but depends on your return details but hopefully this helps point you in the direction of what to look for to tie it out.
