Late to convert 2023 Roth IRA from Traditional IRA :(

Normally I should have done the conversion from my bank account to my traditional IRA and convert from traditional IRA to Roth IRA early the year but I somehow completely forget it this year. I know I screwed it up. And I need some help

 

12/22: initiate transfer $6,500 from my checking account to my traditional IRA in fidelity. Until 12/29, the money is still not cleared and I can't initiate the conversion directly online. I called fidelity services to requet conversion by 12/29 and was told they could help but it was best effort. But it didn't work through. 

12/30: seems the money is clear. and the money become $6,505.40

 

Question:

1. Where the extra $5.40 coming from? Is it taxable or not? 

2. Can I still convert the money to Roth IRA? $6,500 or $6,505.40? Is it counted 2023 or 2024? 

3. What is the tax implication for leave money in traditional IRA? 

 

Thanks and appreciate if any comments.