backport: fix tstamp explanation

v4/content/introduction.html

@@ -388,7 +388,7 @@ <h4 id="timestamps">1.2.3. Timestamps in MEI
 </div>
 
 <p>Sometimes, timestamps are used to indicate positions where no music <em>Events</em> are located (see 
-  <a href="/guidelines/v4/content/introduction.html#eventsControlevents">Events and Controlevents</a>). Therefore, the allowed range of timestamps stretches from 0 to the current meter count + 1. By definition, a timestamp of 1 indicates the position of the left barline, while a timestamp of 5 (in case of a 4/4 meter) indicates the right barline. This makes it possible to encode open-ended slurs in a graphical way. However, it should be kept in mind that such timestamps may not be converted to <em>@startid</em> and <em>@endid</em>, and not every application may be able to render them correctly, even though they are perfectly valid MEI, and sometimes are necessary to faithfully transcribe a source.</p>
+  <a href="/guidelines/v4/content/introduction.html#eventsControlevents">Events and Controlevents</a>). Therefore, the allowed range of timestamps stretches from 0 to the current meter count + 1. By definition, a timestamp of 0 indicates the position of the left barline, while a timestamp of 5 (in case of a 4/4 meter) indicates the right barline. This makes it possible to encode open-ended slurs in a graphical way. However, it should be kept in mind that such timestamps may not be converted to <em>@startid</em> and <em>@endid</em>, and not every application may be able to render them correctly, even though they are perfectly valid MEI, and sometimes are necessary to faithfully transcribe a source.</p>
 
 <h4 id="meiprofiles">1.2.4. MEI Profiles
 

v5/content/introduction.html

@@ -836,7 +836,7 @@ <h3 id="timestamps"><span class="headingNumber">1.3.3</span><span class="head">T
 
                         <p>Sometimes, timestamps are used to indicate positions where no music <em>Events</em> are located (see <a class="link_ptr chapterLink" title="Events and Controlevents" href="../content/introduction.html#eventsControlevents">1.3.2 Events and Controlevents</a>). Therefore, the allowed range of timestamps
                            stretches from 0 to the current meter count + 1. By definition, a timestamp of
-                           1 indicates the position of the left bar line, while a timestamp of 5 (in case
+                           0 indicates the position of the left bar line, while a timestamp of 5 (in case
                            of a 4/4 meter) indicates the right bar line. This makes it possible to encode
                            open-ended slurs in a graphical way. However, it should be kept in mind that
                            such timestamps may not be converted to <span class="att">startid</span> and