How is tax calculated for 1099-DIV for 2020?

Hello,

 

I mistyped Box 1b for one of my 1099-DIVs. It was supposed to have been $100.00 but I accidentally entered in $10,000. When I updated the amount, my tax owned went from $10,300 to $10,900. Does that seem correct? It's my understanding that the tax calculated for a 1099-DIV is Box 1a minus Box 1b. My Box 1a is $1,300 and Box 2a of Total Capital Gain Distributions is $800. Would the tax owned for this one 1099-DIV be as simple as 1,300 minus 100 and then 15% of that amount? Then, what is the actual tax rate for the Total Capital Gain Distributions?

 

Thank you.