diff --git a/Assets/BMapBindings/bmap-rs/README.md b/Assets/BMapBindings/bmap-rs/README.md
index 537f6d9..b25f183 100644
--- a/Assets/BMapBindings/bmap-rs/README.md
+++ b/Assets/BMapBindings/bmap-rs/README.md
@@ -34,3 +34,10 @@ This project will find it in `build.rs` script and tell Rust compiler how to lin
 > You also may need rename some contents of other files involving this rename change.
 
 Also due to this, when distributing your Rust project, please do not forget copy the built BMap library with your Rust artifacts.
+
+## Test
+
+The test code located in `tests` directory is NOT designed for plain "cargo test".
+It is more close to an independent test program, so executing it may require some extra work.
+First you need configure all environment variables for testing.
+Then you can execute `cargo test complete -- --nocapture` to run the complete test program.
diff --git a/Assets/BMapBindings/bmap-rs/src/bmap_wrapper.rs b/Assets/BMapBindings/bmap-rs/src/bmap_wrapper.rs
index 431aabf..c6ba7d1 100644
--- a/Assets/BMapBindings/bmap-rs/src/bmap_wrapper.rs
+++ b/Assets/BMapBindings/bmap-rs/src/bmap_wrapper.rs
@@ -3,7 +3,6 @@
 //! This module is what user of this library should use.
 
 mod marshaler;
-//mod utilities;
 
 use crate::bmap::{self, BMBOOL, CKDWORD, CKID, CKINT, CKSTRING, CKWORD, PBMVOID};
 use std::cmp::Ordering;
@@ -322,7 +321,7 @@ macro_rules! libiter_len_body {
         if $current_cnt >= $all_cnt {
             0
         } else {
-            $current_cnt - $all_cnt
+            $all_cnt - $current_cnt
         }
     };
 }
@@ -332,7 +331,7 @@ macro_rules! libiter_size_hint_body {
         if $current_cnt >= $all_cnt {
             (0, Some(0))
         } else {
-            let remaining = $current_cnt - $all_cnt;
+            let remaining = $all_cnt - $current_cnt;
             (remaining, Some(remaining))
         }
     };
diff --git a/Assets/BMapBindings/bmap-rs/src/bmap_wrapper/utilities.rs b/Assets/BMapBindings/bmap-rs/src/bmap_wrapper/utilities.rs
deleted file mode 100644
index d392d8c..0000000
--- a/Assets/BMapBindings/bmap-rs/src/bmap_wrapper/utilities.rs
+++ /dev/null
@@ -1,4 +0,0 @@
-//! BMap wrapper used utility stuff
-
-
-