Toast displays 2 times | SvelteKit

I'm using SvelteKit and this library to display toast notifications.
Making a project I discovered that calling any notifier function from the onMount of Svelte will duplicate the toast.

Steps to reproduce bug:

npm create svelte@latest 
my-app
cd my-app
npm install
npm i -D @beyonk/svelte-notifications
npm run dev

Paste the following code in the main +page.svelte:

<script>
    import { NotificationDisplay, notifier } from '@beyonk/svelte-notifications'
    import { onMount } from "svelte"
    let n

    onMount(()=>{
        notifier.success('test1', 7000)
        notifier.success('test2', 7000)
        console.log('test1')
        console.log('test2')
    })
</script>

<NotificationDisplay bind:this={n} />

[antony]

interesting. we don't tend to call this from onMount, which is why we probably haven't encountered this issue.

I see. By the way this is still not solved yet.
To go further with my project I decided to change component and I used an other one.

[tamerh]

I am also getting duplicate displays