How did you book your cruise.. directly with HAL, via an external TA? Depending on this information, your dining arrangements (i.e., Fixed early/late or open) should be noted in the 'cruise details' section of your emailed booking confirmation from HAL.
If through a TA, they should have the same information and you need to get it from them. If they don't have it, they can contact HAL on your behalf and get the info.