Arcanist spells prepared, and spells castable per day do not display correctly on spellbook pages, however I believe this to be only a display issue as the correct data DOES exist, but in the wrong places (see below). I will use a level 8 arcanist in my example because thats the character the player in my campaign is using, but the issue exists globally for arcanist.
Per the rules, an arcanist of Level 8 should be able to Prepare 8/5/3/2/1 spells (levels 0 through 4), as per the spells per day table. This is not modified by ability scores, but may be modified by any feats, etc which would normally increase a wizards spells known (since Arcanists can by default know any number of spells and the rules state that for arcanists these feats instead increase spells prepared)
That same arcanist would be able to CAST -/4/4/4/2 spells per day (level 0 through 4), however this does get modified by Intelligence, so if that level 8 arcanist has an Int of 19, they get +1 spells per day of levels 1 through 4, for a total Castable per day of -/5/5/5/3
In PCGen, the arcanist spellbook lists PER DAY as the numbers that really should be Prepared spells (8/5/3/2/1). However the Prepared Spells list that prints out is also correct.
I did notice though, that the class feature "Arcanist Spells Prepared" shows in its description the correct numbers for the actual amount castable per day (-/5/5/5/3) which means that the right data is out there, its just not being displayed on the spellbook pages or under the proper headings.
Ive temporarily worked around this with a custom outputsheet, replacing common-spells.ftl with a modified version that displays things the way they should be, but the "Per day" spell usage is hard coded since im not sure which bucket has the correct data in it.
Windows 10, multiple system configurations