Getting error in IF condition (We cannot apply field access to the type Number)

Hi

I am creating a custom column using the below IF Condition, syntax shows no error. However, an error is coming in the custom column

this is my query

if[Hour] >= 0  [Hour] <= 6 then "1 AM -6 AM" else

if[Hour] >= 6 and [Hour] <= 12 then "6 AM -12 PM" else


if[Hour] >= 12 and [Hour] <= 4 then "12 PM -4 PM" else


if[Hour] >= 4 and [Hour] <= 10 then "4 PM -10 PM" 
else "10 PM - 12 AM"

The error I am getting,

Please advise