Add note that a Big is created from a numbers toString value

docs/index.html

@@ -151,9 +151,8 @@ <h1>big.js</h1>
     <h2>API</h2>
 
     <p>
-      In all examples below, <code>var</code> and semicolons are not shown, and
-      if a commented-out value is in quotes it means <code>toString</code> has
-      been called on the preceding expression.
+      For brevity, <code>var</code>, semicolons and <code>toString</code> calls
+      have been omitted in the examples below.
     </p>
 
 
@@ -169,6 +168,12 @@ <h5 id="big">
       but if <a href='#strict'><code>Big.strict</code></a> is set to <code>true</code>
       an error will be thrown if <code>n</code> is not a string or Big number.
     </p>
+    <p>
+      Note that primitive numbers are accepted purely as a convenience so that quotes
+      don't need to be typed for numeric literals of up to 15 significant digits, and
+      that a Big number is created from a number's <code>toString</code> value rather
+      than from its underlying binary floating point value.
+    </p>
     <p>
       <code>Infinity</code>, <code>NaN</code> and hexadecimal literal
       strings, e.g. '0xff', are <u>not</u> valid.
@@ -178,21 +183,20 @@ <h5 id="big">
       e.g. '011' is 11, not 9.
     </p>
     <p>
-      String values may be in exponential, as well as normal (non-exponential)
-      notation.
+      String values may be in exponential, as well as normal notation.
     </p>
     <p>
       There is no limit to the number of digits of a <em>string</em> value
       (other than that of JavaScript's maximum array size), but the largest
       recommended exponent magnitude is 1000000.
     </p>
-    <p>Returns a new Big number object with value <code>n</code>.</p>
+    <p>Returns a new Big number with value <code>n</code>.</p>
     <p>Throws if <code>n</code> is invalid.</p>
     <p>
       Using <code>new</code> with Big is optional, but note that if no argument
       is passed when doing so, or if the argument is <code>undefined</code>,
-      then a new Big constructor will be returned rather than a new Big number
-      instance. See <a href='#multiple'>creating additional Big number constructors</a>
+      then a new Big constructor will be returned rather than a new Big number.
+      See <a href='#multiple'>creating additional Big number constructors</a>
       below.
     </p>
     <pre>