There is nothing “Number-Variable like” about a Number Item. Items are complex Objects with lots of moving parts and the Number Item just happens to carry a State that is a Number.
To change the state of an Item you must use either sendCommand or postUpdate. This is the only way to change the state of an Item.
I don’t understand this statement. I and others do math with and update the results from calculations using postUpdate and sendCommand all the time. Please review:
and if that doesn’t solve your problem post your code.