I believe the Iowa Form IA 1040 has an error. When itemizing charitable contributions on Iowa Sch A, you should be excluding the $300 deduction taken on line 24.

[TECRUN]

Instead, line 14 of IA 1040 Sch A is not reduced by this adjustment. The 2020 IA Form 1040 instructions states that it should be.

[SamS1]

You are correct.  The amount of the adjustment to income on the Iowa return should be reducing the total charitable contributions on the Schedule A.   At this point, it is manual adjustment.  If you are using Desktop, go into forms mode by clicking on "Forms" in the upper right hand corner.  The open the IA Sch A and decrease the amount of charitable cash contributions by the amount of the charitable adjustment to income on page 1 of the IA 1040.  If you are using TurboTax Online, there will be a question in the Iowa state return regarding reducing your charitable contribution deduction on the  IA Sch A.

[Twinklm]

Any estimate on when this issue will be fixed?

[SamS1]

Not at this time.  All resources are being used to get the recent American Rescue Plan Act changes made and implemented into TurboTax.  Its been a crazy tax year with so many changes coming from all directions  This will have to be a manual adjustment for now.  I did note the 8915E retirement plan deferral was implemented into the Iowa return. In previous versions the total Covid distribution was coming across as income on the Iowa return instead of just 1/3.

The American Rescue Plan was signed into law on March 11. This will include a third stimulus package. If you had issues receiving your earlier stimulus, then the best way to ensure that you are one of the first to receive future stimulus payments is to file your 2020 tax return as early as possible and use direct deposit so that the IRS will have your updated information. 
 
You can find the most up to date information from the IRS here, and read more from TurboTax here.