Actually this is where ME2's morality system turns into a fucking mess.
See, it's not actually based on the points you accumulate, but rather the percentage of your overall paragon/renegade score. So if a check is looking for a 75% renegade score, it's looking if 75% of your total score consists of renegade points. It's really confusing, and it's how you can fail speech checks even with high scores. To name an example, Zaeed's mission requires a high paragon score if you do the paragon path and want his loyalty. It's ironically better to do it early on because if you do it later you might have that small percentage of renegade actions prevent you from passing the check.
None of this is adequately explained in-game either, I only found out thanks to the wiki. It certainly explains why the morality system can be weird and inconsistent across various playthroughs, especially in contrast to 1 and 3.