How does evidence in this document show that “Kristallnacht” was planned in advance of the event actually happening?

TO ALL REGIONAL AND SUB-REGIONAL GESTAPO OFFICES
sent at 1:20AM, November 8, 1938

SUBJECT: MEASURES AGAINST THE JEWS THIS NIGHT
That only such measures were to be taken that would not endanger German lives or property (e.g. the burning of synagogues was only to be carried out if there was no danger of fire spreading to the surrounding district).  Businesses and residences of Jews may be damaged but not looted. Particular care is to be paid in business sections and surrounding streets. Non-Jewish businesses are to be protected from damage under all circumstances. Police are to seize all archives from synagogues and offices of community organizations, this refers to material of historical significance. Archives are to be handed over to the SS. As soon as possible, officials are to arrest as many Jews especially wealthy ones - in all districts as can be accommodated in existing cells. For the time being, only healthy male Jews of not too advanced age are to be arrested.

 Signed by Reinhard Heydrich,
SS Gruppenfürer

 How does evidence in this document show that “Kristallnacht” was planned in advance of the event actually happening?

Because the letter was sent the day before Kristallnacht was launched