The switch's script will only be executed when its value changes, not when the osc listener (the OSC{} block) receives a value, so this won't work (there's also a syntax error: missing closing parenthesis after "> 8").
You could achieve what you want by writing this int the switch's value
property:
JS{{
if (OSC{/track/number/str} > 8) {
return 2
}
}}
or you could create a script widget with address
set to /track/number/str
and script
to:
if (value > 8) {
set("Bank", 2)
}