You can't put the same in the equation, now I don't know how to correct it.
double-click the quota, enter the quota editor and copy this string instead of the numerical value
=iff("d1@schizzo1"<300 , 160) , iff("d1@schizzo1"<300 .1, 192)
It's part of the condition.
I try to translate the formula
=iif("d1@schizzo1"<300 , 160 , iif("d1@schizzo1"<300.1, 192, 100 ))
if d1 is less than 300 then put the quota at 160, if d1 is greater than 300,1 then put the quota at 192, otherwise put the quota at 100
you must always put an alternative condition to that request
maybe you can try to simplify by removing an iif saying that if d1 is less than 300 then put the quota at 160, otherwise whatever the value of d1 put it at 192
=if("d1@schizzo1"<300 , 160 , 192)