It’s not random, these are the SRS times for items:
| SRS Level | Next Level | Total Wait | Review |
|---|---|---|---|
| Apprentice 1 | 4h | - | Lesson |
| Apprentice 2 | 8h | 4h | 1 |
| Apprentice 3 | ~1d | 12h | 2 |
| Apprentice 4 | ~2d | 1d 11h | 3 |
| Guru 1 | ~1w | 3d 10h | 4 |
| Guru 2 | ~2w | 1w 3d 9h | 5 |
| Master | ~1M | 3w 3d 8h | 6 |
| Enlightened | ~4M | 7w 5d 7h | 7 |
| Burned | - | 24w 6d 6h | 8 |
So depending on the time of day you do lessons/reviews, the srs level that the items are at (ex apprentice items will show up more frequently), the # of items you get correct vs incorrect, etc, will all determine the timeline of your upcoming reviews
Maybe installing the Ultimate Timeline script will help you visualize what to expect ^^