[Vuejs]-Typescript: getting right-hand side arithmetic error

Because, Typescript try to warn you: Do not do some math with strings?

  // computedNode's properties are strings
  const computedNode = {
    height: '20px',
    paddingTop: '8px', 
    paddingBottom: '8px'
  }
  
  const coversContainerHeight = (computedNode.height - (computedNode.paddingTop + computedNode.paddingBottom));