How to use the @deja-js/component/popup.DejaPopupConfig.dialogCount function in @deja-js/component

public showPopUpPdf() {
        const config = new DejaPopupConfig();
        config.title = `Pdf ${DejaPopupConfig.dialogCount}`;
        config.url = this.dummyPdfUrl;
        config.padding = false;
        config.toolbarIconName = 'photo_camera';
        config.toolbarColor = 'accent';

        config.toolbarActions = [
            new DejaPopupButton('account', 'User', 'account_circle', false),
            new DejaPopupButton('view', 'Show', 'visibility', false),
        ];

        config.ensureDimension();

        this.dejaPopupService.openPopUp(config).pipe(
            filter((resp: DejaPopupReponse) => !!resp))
            .subscribe((response: DejaPopupReponse) => {
                this.showResponse(response);