Minor typo fix

Author: Mich

src/mainwindow.ui

@@ -2278,7 +2278,7 @@ p, li { white-space: pre-wrap; }
                        </size>
                       </property>
                       <property name="whatsThis">
-                       <string>&lt;html&gt;&lt;head/&gt;&lt;body&gt;&lt;p&gt;Sets the missing samples threshold value. If process string doesnt contain related data n times in a row it is then automatically deleted.&lt;/p&gt;&lt;/body&gt;&lt;/html&gt;</string>
+                       <string>&lt;html&gt;&lt;head/&gt;&lt;body&gt;&lt;p&gt;Sets the missing samples threshold value. If processed string doesnt contain one new data for the already present graph n times in a row it is then this graph will be automatically deleted. This is useful when switching between diffrent steaming data sets.&lt;/p&gt;&lt;/body&gt;&lt;/html&gt;</string>
                       </property>
                       <property name="alignment">
                        <set>Qt::AlignCenter</set>