more benchmark.md fixes

bench/benchmarks.md

@@ -6,7 +6,6 @@ with `compression_level` 8.
 Speeds are reported in count of numbers compressed or decompressed
 per second with 2 significant figures.
 Compression ratio is reported with 3 significant figures.
-For the `i64` heavy-tail integers, a Lomax distribution with alpha parameter 0.5 and median 1000 was used.
 
 | dataset            | compression speed / (million/s) | decompression speed / (million/s) | compression ratio |
 |--------------------|---------------------------------|-----------------------------------|-------------------|
@@ -16,12 +15,9 @@ For the `i64` heavy-tail integers, a Lomax distribution with alpha parameter 0.5
 | `i64_sparse`       | 36                              | 220                               | 792               |
 | `micros_millis`    | 11                              | 120                               | 2.08              |
 
-`i64` and `f64` are each 8 bytes, so for the more interesting distributions
-(e.g. heavy-tail integers and standard normal),
-this is a decompression speed of 300-400MB/s.
-
+`i64` and `f64` are each 8 bytes, so these speeds are in the ballpark of 1GB/s.
 For reference, on the same hardware and heavy-tail integers dataset, ZStandard
-`0.10.0+zstd.1.5.2` gets:
+`0.12.3+zstd.1.5.2` gets:
 
 * level 3: compresses 13 million/s, decompresses 52 million/s, compression
 ratio 3.14.