해결됨

<template>
  <div>
-    <Counter count="1"/>
-    <Counter count="2"/>
-    <Counter count="3"/>
+    <Counter :count="1"/>
+    <Counter :count="2"/>
+    <Counter :count="3"/>
  </div>
</template>

Code

<template>
  <div>
    <Counter count="1"/>
    <Counter count="2"/>
    <Counter count="3"/>
  </div>
</template>

<script>
import Counter from '~/components/Counter.vue'

export default {
  components: {
    Counter
  }
}
</script>

<template>
  <div>
    <h2>
      Count: {{ count }}
    </h2>
    <input type="button" @click="incrementCounter" value="Increment!">
  </div>
</template>

<script>
export default {
  props: {
    count: {
      type: Number,
      default: 1
    },
  },
  methods: {
    incrementCounter (e) {
      this.count = this.count + 1
    }
  }
}
</script>

Original by Github issue