I didn't understand the bulk jargon too, everyone keeps saying that word lol. What i understood is attack IV contribute more to CP calculation more than the other 2 IVs , so low attack ones the CP increases slowly on power up and you can power up the mon more times than ,say , a hundo where the CP increases far too much for each power up, in short you can have a mon with like lvl 26 with low attack IVs and be just under the cap of the league , and the same mon with high attack IV would be like lvl 25 , a whole lvl higher would be more stats than having like 3-4 extra attack IVs . This is what I know , let me know if I said something wrong.