This is the closest I was able to get (attached as well). I don't think there is a way with Quest to offset a room. It seems to always draw centered on the exit.
I just inserted a narrow room down the center (to even out the rooms and give a center exit). Might not be what you want, but just in case it's a viable approach...
<!--Saved by Quest 5.6.5621.18142-->
<asl version="550">
<include ref="English.aslx" />
<include ref="Core.aslx" />
<game name="mappy">
<gameid>b8447cb8-acaf-4d6b-8aa9-10326d5398d0</gameid>
<version>1.0</version>
<firstpublished>2015</firstpublished>
<gridmap />
</game>
<object name="behind counter">
<inherit name="editor_room" />
<attr name="grid_width" type="int">8</attr>
<attr name="grid_length" type="int">4</attr>
<object name="player">
<inherit name="editor_object" />
<inherit name="editor_player" />
</object>
<exit alias="east" to="hallway">
<inherit name="eastdirection" />
<attr name="grid_length" type="int">0</attr>
</exit>
</object>
<object name="lounge">
<inherit name="editor_room" />
<attr name="grid_width" type="int">8</attr>
<attr name="grid_length" type="int">4</attr>
<exit alias="west" to="hallway">
<inherit name="westdirection" />
<attr name="grid_length" type="int">0</attr>
</exit>
</object>
<object name="Main Office">
<inherit name="editor_room" />
<attr name="grid_width" type="int">17</attr>
<attr name="grid_length" type="int">9</attr>
<exit alias="north" to="hallway">
<inherit name="northdirection" />
<attr name="grid_length" type="int">0</attr>
</exit>
</object>
<object name="hallway">
<inherit name="editor_room" />
<attr name="grid_length" type="int">4</attr>
<exit alias="west" to="behind counter">
<inherit name="westdirection" />
<attr name="grid_length" type="int">0</attr>
</exit>
<exit alias="east" to="lounge">
<inherit name="eastdirection" />
<attr name="grid_length" type="int">0</attr>
</exit>
<exit alias="south" to="Main Office">
<inherit name="southdirection" />
<attr name="grid_length" type="int">0</attr>
</exit>
</object>
</asl>