What the score represents
The 0 to 100 score summarizes weighted issue density. Serious broken paths and indexation problems reduce it more than housekeeping findings. The calculation also accounts for site size so one defect on a very small site does not overwhelm the full result.
What the score does not represent
It is not a Google metric, a ranking forecast, or a substitute for reviewing affected URLs. Two sites with the same score may carry very different risks. Use it to locate change, then read the issue mix.
How to report movement
Explain the score beside crawled page count, high-severity issue count, and scope. A credible update says what changed and why, not only that a number rose.