There is a difference in the default alignment of the tables content when the table is located in the package-info.java or in some other places.
In the code below there are two tables which have the same styles(some default), but look differently:

package-info.java
==========================================
/**
 * Some description....
 *
 * <table>
 * <caption>CAPTION</caption>
 * <tr>
 * <th>X1_____<br>X1_____
 * <th>X2
 * <th>X3
 * <tr>
 * <td>Y1
 * <th>Y1_____<br>y1_____
 * <td>Y3
 * <tr>
 * <td>Z1
 * <td>Z2
 * <th>Z1_____<br>Z1_____
 * </table>
 */
package javadoc;
==========================================

SomeClass.java
==========================================
package javadoc;

/**
 * Some description....
 *
 * <table>
 * <caption>CAPTION</caption>
 * <tr>
 * <th>X1_____<br>X1_____
 * <th>X2
 * <th>X3
 * <tr>
 * <td>Y1
 * <th>Y1_____<br>y1_____
 * <td>Y3
 * <tr>
 * <td>Z1
 * <td>Z2
 * <th>Z1_____<br>Z1_____
 * </table>
 */
public class SomeClass {

}
==========================================

Please take a look to alignments and indents.

Links for convenience
 - http://cr.openjdk.java.net/~serb/tmp/doc/javadoc/package-summary.html
 - http://cr.openjdk.java.net/~serb/tmp/doc/javadoc/SomeClass.html