The “7 Stars Robbery” in Xuan Kong Da Gua (玄空大卦) adopt the concept of “Inverted Hexagrams (綜卦)”.
For example, when a given Hexagram is read upside
down, we get this “Inverted Hexagram”. That relate to another set of Gua Qi (卦氣) and Gua Yun (卦運).
It is believe that the original Hexagram and its inverted version is one and the same Hexagram read from different (opposite) vantage points. And hence, the “Inverted Hexagram” therefore maintains a connection with the original Gua and Palace. Even though the inverted Hexagram may reside at a different Palace.
For example changing the current Gua Yun (卦運) from a period 6 to period 8. Having said that, the reverse should also be true, for example my current Gua Yun (卦運) is period 8 and accidentally activated a period 6 Gua Yun (卦運).
Note that not all Gua can be inverted. Out of the 64 Gua, there are 8 Gua in particular that are unable to be Inverted (B’cos the Gua Qi (卦氣) and Gua Yun (卦運) are of the same numbers ~ layman speaking)
The value add of “7-Stars Robbery” in Xuan Kong Da Gua (玄空大卦) lies in its ability to make good use of Hexagrams that are untimely, thru the associated connection between the Original Gua and “Inverted Hexagrams (綜卦)”.
In summary, not all the Gua Yun (卦運) can be change. A handful of the Gua (even though) can be “Inverted Hexagrams (綜卦)” they still end up with the same Gua Yun (卦運). Moreover, the Inverted Gua don’t crosses between the upper yuan (上元) and or lower yuan (下元). Hence, won’t affect the direct and/or indirect spirit.