Nuxt 3 sometimes I can omit .value when using useState, sometimes I can’t, why?

Please see this minimum example, if I use useState , normally, I can write something like this:

<script setup>
const num = useState('num', () => 1);
</script>

<template>
  <div>
    {{ num }}
  </div>

  <div>
    {{ typeof num }}
  </div>

  <div>
    {{ JSON.stringify(num) }}
  </div>
</template>

And the result is what I expected:

1
number
1

However, when I move the useState into composables, everything changed, like this:

export const useNum = () => {
  const num = useState('num', () => 1);

  return {
    num,
  };
};

<script setup>
const numStore = useNum();
</script>

<template>
  <div>
    {{ numStore.num }}
  </div>

  <div>
    {{ typeof numStore.num }}
  </div>

  <pre>
    {{ JSON.stringify(numStore.num, null, 2) }}
  </pre>
</template>

the result is super weird:

1
object
    {
  "_object": {
    "$s__nuxt_devtools__": {
      "timeSsrStart": 1719387436211
    },
    "$snum": 1
  },
  "_key": "$snum",
  "__v_isRef": true
}
  

Why is this happening? How can I avoid this?