counter(page) is invalid

[Kujo-Jotaro-AAAAA]

hello ~
why counter(page) is invalid ， Always 0 ?

`

<title>Document</title>

Clients report

Annual Report of our Company

Address: William Road

页码:

Client

<p>Name: ${client.fields.title}</p>
<p>Summary: ${client.fields.summary}</p>

`

`body {
font: 12pt Georgia, "Times New Roman", Times, serif;
line-height: 1.3;
}

@page {
/* switch to landscape /
size: A4;
/ set page margins /
margin: 0.5cm;
/ Default footers */
@bottom-left {
content: "Department of Strategy";
}
@bottom-right {
content: counter(page) " of " counter(pages);
}
}

/* footer, header - position: fixed */
#header {
position: fixed;
width: 100%;
top: 0;
left: 0;
right: 0;
}

#footer {
position: fixed;
width: 100%;
bottom: 0;
left: 0;
right: 0;
}

/* Fix overflow of headers and content */
body {
padding-top: 50px;
}
.custom-page-start {
margin-top: 50px;
}

.custom-footer-page-number:after {
content: counter(page) counter(pages);
}
`