When the maximum value is 100 the line of the part of the graph is of a smaller thickness.

The value cannot be more than 100.

yAxis: {
        title: {
            text: ''
        },
        tickAmount: 5,
        labels: {
            format: '{value}%',
            style: {
                color: 'var(--el-text-color-primary)'
            }
        },
        min: 0,
        max: 100
    }```