I think this is describing a direct rollover from a 401(k) to an inherited IRA (codes 4 and G in box 7 of the Form 1099-R).
Because your husband's mother was still working for this employer, she died before her required beginning date for RMDs. Tell TurboTax that none of this distribution was RMD and that no RMD was required with respect to this 401(k).
Regarding beneficiary RMDs that your husband will be required to take, proposed regulations that the IRS issued last week indicate that this account will be subject to both the 10-year rule and annual RMDs. It's not clear if this will change in the final regulations since the IRS seems to have gone back an forth on whether annual RMDs are required in this case under the 10-year rule.
