Their explanation is nonsensical. A form 1099-R with code G in box 7, the IRA/SEP/SIMPLE box marked and a nonzero amount in box 2a reports what is essentially an illegal transaction, a rollover from a traditional IRA to a designated Roth account in an employer plan, not to a Roth IRA.
The proper approach would be to submit a substitute Form 1099-R (Form 4852) showing code 2 (under age 59½) or code 7 (age 59½ or over) in box 7 and provide explanation. However, filing a substitute Form 1099-R requires printing and mailing your tax return. Alternatively, you could simply change the code to code 2 or code 7 and enter without claiming it to be a substitute Form 1099-R as fanfare suggests, then wait and see if the IRS questions it, at which time you could provide explanation.
