diff --git a/src/main.rs b/src/main.rs
index 999706de..9c112be6 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -230,12 +230,12 @@ fn main() {
         .after_help("Optimization levels:
     -o 0   =>  --zc 3 --nz                  (0 or 1 trials)
     -o 1   =>  --zc 9                       (1 trial, determined heuristically)
-    -o 2   =>  --zc 9 --zs 0-3 -f 0,5       (8 trials)
-    -o 3   =>  --zc 9 --zs 0-3 -f 0-5       (24 trials)
+    -o 2   =>  --zc 9 --zs 0-3 -f 0,5       (8 trials with zlib or 2 trials with other compressors)
+    -o 3   =>  --zc 9 --zs 0-3 -f 0-5       (24 trials with zlib or 6 trials with other compressors)
     -o 4   =>                               (deprecated; same as `-o 3`)
-    -o 5   =>  --zc 3-9 --zs 0-3 -f 0-5     (96 trials)
-    -o 6   =>  --zc 1-9 --zs 0-3 -f 0-5     (180 trials)
-    -o max =>                               (alias for the max compression, currently same as -o 6)
+    -o 5   =>  --zc 3-9 --zs 0-3 -f 0-5     (96 trials with zlib; same as `-o 3` for other compressors)
+    -o 6   =>  --zc 1-9 --zs 0-3 -f 0-5     (180 trials with zlib; same as -o 3` for other compressors)
+    -o max =>                               (stable alias for the max compression)
 
     Manually specifying a compression option (zc, zs, etc.) will override the optimization preset,
     regardless of the order you write the arguments.")