Tickscript using Sigma i see Field value mismatch with message

I am using the following tickscript to alert using sigma (standard deviation) and i am seeing a huge number of value mismatch.

Field “Percent_Processor_Time_Sigma” in message and in itself populates different values, why is that?

var db = ‘test’

var rp = ‘autogen’

var measurement = ‘Process’

var groupBy = [‘instance’, ‘host’]

var whereFilter = lambda: (“instance” != ‘Idle’)

var message = ‘{{ if eq .Level “OK” }} “Percent_Processor_Time_Sigma is Less than 1, value : {{ index .Fields “Percent_Processor_Time_Sigma” }}” {{ else }} “Percent_Processor_Time_Sigma is Greater than 1, value : {{ index .Fields “Percent_Processor_Time_Sigma” }}” {{ end }}’

var process = stream
|eval(lambda: sigma(float(“Percent_Processor_Time”)))
.crit(lambda: “Percent_Processor_Time_Sigma” >= 1)

This can be solved by using a selector example “last”.