Document changes to benchmarking + print number of threads for displa…

…y level >= 2

programs/zstd.1.md

@@ -343,7 +343,7 @@ If the value of `ZSTD_CLEVEL` is not a valid integer, it will be ignored with a
 
 `ZSTD_NBTHREADS` can be used to set the number of threads `zstd` will attempt to use during compression.
 If the value of `ZSTD_NBTHREADS` is not a valid unsigned integer, it will be ignored with a warning message.
-`ZSTD_NBTHREADS` has a default value of (`min(4, nbCores/4`), and is capped at ZSTDMT_NBWORKERS_MAX==200.
+`ZSTD_NBTHREADS` has a default value of (`min(4, nbCores/4)`), and is capped at ZSTDMT_NBWORKERS_MAX==200.
 `zstd` must be compiled with multithread support for this variable to have any effect.
 
 They can both be overridden by corresponding command line arguments:
@@ -664,9 +664,12 @@ BENCHMARK
 The `zstd` CLI provides a benchmarking mode that can be used to easily find suitable compression parameters, or alternatively to benchmark a computer's performance.
 `zstd -b [FILE(s)]` will benchmark `zstd` for both compression and decompression using default compression level.
 Note that results are very dependent on the content being compressed.
+
 It's possible to pass multiple files to the benchmark, and even a directory with `-r DIRECTORY`.
 When no `FILE` is provided, the benchmark will use a procedurally generated `lorem ipsum` text.
 
+Benchmarking will employ `min(4, nbCores/4)` worker threads by default in order to match the behavior of the normal CLI I/O.
+
 * `-b#`:
     benchmark file(s) using compression level #
 * `-e#`: