Patched typo in Java Long max value

Author: velias

content/documentation/master/schema.md

@@ -310,7 +310,7 @@ Extended graphql-java scalars
 * ``GraphQLBigDecimal``
 * ``GraphQLBigInteger``
 
-Note that the semantics around the extended scalars might not be understood by your clients.  For example mapping a Java Long (max value 26^3-1) into a JavaScript Number ( max value 2^53 - 1)
+Note that the semantics around the extended scalars might not be understood by your clients.  For example mapping a Java Long (max value 2^63-1) into a JavaScript Number ( max value 2^53 - 1)
 may be problematic for you.