Update print.md (#1597)

On the website, there are two options listed for hexadecimal. I was confused what the difference between the capital x and X was but then I ran it through and realized the latter capitalized the letters. I've also done the courtesy of listing out their subsequent results.

I also added some additional information to the "width" section and formatted it for easier readability.

src/hello/print.md

@@ -31,17 +31,20 @@ fn main() {
 
     // Different formatting can be invoked by specifying the format character after a
     // `:`.
-    println!("Base 10 repr:               {}",   69420);
-    println!("Base 2 (binary) repr:       {:b}", 69420);
-    println!("Base 8 (octal) repr:        {:o}", 69420);
-    println!("Base 16 (hexadecimal) repr: {:x}", 69420);
+    println!("Base 10:               {}",   69420); //69420
+    println!("Base 2 (binary):       {:b}", 69420); //10000111100101100
+    println!("Base 8 (octal):        {:o}", 69420); //207454
+    println!("Base 16 (hexadecimal): {:x}", 69420); //10f2c
+    println!("Base 16 (hexadecimal): {:X}", 69420); //10F2C
 
-    // You can right-align text with a specified width. This will output
-    // "    1". 4 white spaces and a "1", for a total width of 5.
+
+    // You can right-justify text with a specified width. This will
+    // output "    1". (Four white spaces and a "1", for a total width of 5.)
     println!("{number:>5}", number=1);
 
-    // You can pad numbers with extra zeroes. This will output "00001".
-    println!("{number:0>5}", number=1);
+    // You can pad numbers with extra zeroes,
+    //and left-adjust by flipping the sign. This will output "10000".
+    println!("{number:0<5}", number=1);
 
     // You can use named arguments in the format specifier by appending a `$`
     println!("{number:0>width$}", number=1, width=5);