How to use FFXII The Zodiac Age RNG manipulator tool (not made by me):
LINK TO DETAILED INSTRUCTIONS (download link to RNG manipulation tool is also there)
Instruction snippet:
Character stats and platform: this is straightforward. For manipulation you tend to use just one character, using Cure, so put your level and magick power stat in and leave Cure selected. If your character has Serenity as a license/augment, select the box. This also applies to whether you have Magick Gloves equipped (same effect as Serenity). Make sure to select PS4 as platform.
Finding your position: this is the first thing you need to do in order to begin RNG manipulation. Place yourself just before the zone entry to the area with the chest you want to spawn. Remove your weapons, but leave your armor on (more on this later), and remove any equipment that provides status changes (and remove any current). Make sure you are full HP. Cast Cure on yourself. In the FF12RNGH app, enter the healed amount in the "Last healed for:" box, and click "Begin search". Cast Cure on yourself 3 more times, each time putting the healed amount in the box, and clicking "Continue". This should be enough to find your current position in the table. Whatever your most recent Cure value was (under heal) will be your current position.