Minor Child inherited IRA Question

A minor child inherited an IRA totaling $20,800. It was cashed out and placed in minor child investment account. The minor child (age 13) received a 1099-R with Distribution Code 4.

20% tax was withheld. When doing a tax return for minor claiming that they are claimed as a dependent on their parents' return, the software assesses a 44.7% effective tax rate on this "income".

Parents filed M filing J. They have $134k in combined income. Does the tax rate on the child's income seem correct? That's a hefty tax on $20k ($8692). Is there any strategy for lowering this tax rate?