You will see a question asking for your anticipated marathon finish time (like this):
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If you answer above whatever the cutoff is for the marathon (let's say 4:15 for sake of an example), then you'll see a question like this where you choose a range for an estimate:
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However, if you select under 4:15, then you will be prompted to input a POT (for which a marathon POT needs to be a 10 miler, HM or Marathon as
@jmasgat said). But you will not be asked for an estimated pace block (like non-POT are doing) for the HM/M if you input a POT. In the past, they used to do both a POT and an estimated pace block, but people were being seeded by the estimated pace and not what the POT said they were capable of. So despite qualifying for "A" corral by POT, if they said they actually planned on running a 5:00 hours estimated finish, then they were seeded at 5:00 hours. Some people got upset because they wanted the buffer on race day that the POT would grant them. So runDisney eventually got rid of that duel question.
Now, after a POT submission for HM/M portion of Dopey, you'll also see the following question:
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So you will be separately seeded for the 5k/10k based on the answer to this question.
*Keep in mind, all of this can be changed after registration up to POT cutoff day (October 2021). So don't fret/waste your time on this during actual registration. You can edit this at a later time (like right after securing your bib).