For 2018, the developer mangled the wording of this question. It's actually asking, "Did you inherit this IRA which is held by <Insert Financial Institution> as custodian?"
If the assets were transferred directly into an inherited IRA, trustee-to-trustee, there should have been no code 4 Form 1099-R issued. A trustee-to-trustee transfer is neither a distribution nor a rollover. A code 4 Form 1099-R instead implies that there was a distribution paid to you and, as a non-spouse beneficiary you are not permitted to roll the money over to another account. TurboTax knows this so it will not offer you the opportunity to report it as rolled over.
If this truly was a trustee-to-trustee transfer, you must get the custodian of your mother's IRA to correct the code 4 Form 1099-R so show $0 distributed. If the custodian refuses, you'll have to file a substitute Form 1099-R (Form 4852) showing $0 in boxes 1 and 2a in place of the amounts reported by your mother's IRA custodian.
