How to use the @uifabric/fluent-theme.FontSizes.size68 function in @uifabric/fluent-theme

],

    heroSection: [
      classNames.heroSection,
      ...sectionStyles,
      {
        transitionDelay: '0.1s',
        paddingTop: 132,
        paddingBottom: 132
      }
    ],

    heroTitle: [
      classNames.heroTitle,
      {
        fontSize: FontSizes.size68, // @TODO: Mock uses 64
        color: '#cf8fff', // @TODO: Fluent color palette?
        lineHeight: '1.1',
        margin: 0
      }
    ],

    platformCardsSection: [
      classNames.platformCardsSection,
      {
        transitionDelay: '0.2s',
        position: 'relative',

        selectors: {
          '&:before, &:after': {
            content: '""',
            width: '50vw',

cardListItem: [
      classNames.cardListItem,
      {
        display: 'flex',
        justifyContent: 'space-between',
        alignItems: 'center',
        flexWrap: 'wrap',
        lineHeight: '1.6',
        marginBottom: 12
      }
    ],

    cardIcon: [
      classNames.cardIcon,
      {
        fontSize: FontSizes.size68,
        color: palette.black,
        marginBottom: '1em',

        selectors: {
          [mediaQuery.maxMobile]: {
            marginBottom: '.25em'
          }
        }
      }
    ],

    link: [
      classNames.link,
      {
        fontFamily: monoFont,
        display: 'flex',