First off, check if these variables are actually set. If it returns none then it's because the variable probably doesn't have any value (= it isn't set)
You can't use local variables, if you haven't set it yet. Local variables are only variables that exist and must be set during one instance (=event or whatever it is). Outside of that instance the variable doesn't exist, hence why it's local. You often use local variables to save and use information during one specific event, but don't want it to be used across the rest of the server. That variable with it's set value
only exists within
that event.
Btw is the {_combat} supposed to be a PvPTimer or how many kills a player has? You haven't specified what those variables actually are and how you saved them, so it's hard to confirm that the rounding is the problem. I'd would've expected Skript to just round the number to 0 and not display '<none>'.
Here is my spaghetti code for Number Accuracy if that is an issue though, the first number is your variable, the second number is how many decimals you want to see. Else you're going to have to change the number accuracy in the skript options file, but this will change the number accuracy across the rest of skript too, so I prefer to just create a function. So here's how I do it, although probably not the cleanest way:
Code:
function NumberAccuracy(n: number, a: number) :: text:
set {_amount} to rounded ({_n}*10^{_a})
if length of "%{_amount}%" is greater than {_a}:
set {_firstpart} to subtext of "%{_amount}%" from characters 1 to length of "%{_amount}%"-{_a}
set {_secondpart} to subtext of "%{_amount}%" from characters "%{_amount}%"'s length-{_a}+1 to length of "%{_amount}%"
else:
set {_firstpart} to 0
set {_secondpart} to {_amount}
set {_n} to {_a}
remove length of "%{_secondpart}%" from {_n}
loop {_n} times:
set {_secondpart} to "0%{_secondpart}%"
loop {_a} times:
if last character of "%{_secondpart}%" is "0":
set {_secondpart} to subtext of "%{_secondpart}%" from characters 1 to length of "%{_secondpart}%"-1
if {_secondpart} is not set:
set {_return} to "%{_firstpart}%"
else:
set {_return} to "%{_firstpart}%.%{_secondpart}%"
return "%{_return}%"