The truth about ABEC ratings ..... for starters it is an American ratings system that requires physical testing of a large sample of actual bearings by the Annular Bearing Engineers Committee. So, when you see this rating on bearings made elsewhere don't believe the hype. German bearings would be rated by the DIN, and the Japanese by JIS, and others by the ISO.
Not that it matters much for a fishing reel. The ABEC rating is a rating of average tolerances and nothing else. 3 of 10 ABEC 3 bearings will have tolerances tight enough to hit Maximum testing RPM, whereas 7 of 10 ABEC 7 bearings will. So the rating is more of a rating of the assembly line where the bearing is made than it is an individual bearing. You can get a better bearing in a batch of ABEC 3 than you might get in a batch of ABEC 7, but the odds are that you will get the more accurate bearing in the ABEC 7 batch. The rating is more one of consistency of manufacturing rather than a rating of individual bearings. An ABEC-7 rating means that the bearing that you are buying is made on a line where 7 of 10 bearings meet the ABEC-7 spec....however yours might be one of the other 3.
The next thing is that a high ABEC rating is not the same thing as a higher quality bearing. The ABEC standards don't test or measure material quality, quality of the balls, polish, or any other of the many important factors in a bearing.
Finally, does it even make a difference for use in a fishing reel. Not much. For example the allowable difference in the OD of the ABEC-3 and the ABEC-7 bearing is 1/10,000". There is no difference between ABEC-5 and ABEC-7. There is no way that any fishing reel is manufactured at a tighter tolerance than that, so it literally doesn't matter which bearing you use. AND...if there were, you wouldn't likely benefit from that improvement until the spool hit 20,000+ RPM anyway.
If you are interested enough to want to see the actual ABEC specs...look here.
https://www.engineersedge.com/bearing/ball_bearings_tolerances.htm