What does it mean for N1/N2 to float? The logic of ECU to hold N1 with fuel flow follow the logic:

Idle N2------------N2 set ,N1 floats
min ps3 schedule -----------N1 and N2 float


So what does this mean? And does the float here with the same meaning of the float display on the UPPER ECAM?
Float just means that that value will vary depending on ambient temperature pressure etc. It is not controlled. E.g. on n2 control, if n2 goes down then the control puts in more fuel and if n2 goes up then the control puts in less. But if n1 changes (maybe because ambient temp changed ) the control does nothing. If n1 goes down then so be it.