Load Filemanager with initial path +1 level higher than root(dynamic)

Hi. To put you in context have thousands of projects and we only want to display the directory corresponding to a specific project. So for exemple if project is named 8857 we want to open filemanager on the folder name 8857.
Heres my exemple in code:

webix.ready(function () {
	class MyBackend extends fileManager.services.Backend {
		files(id) {
	               return webix.ajax('<%=DirPath%>' + "files", { id })
				.then((data) => data.json());
			     }
	}

var app = new fileManager.App({
	url: "//localhost:3200/",
	override: new Map([[fileManager.services.Backend, MyBackend]]),
	});

app.render(document.getElementById('<%=box.ClientID%>'));
	});

So far this is working its loading the Filemanager at the root of my repo.
Where the backend is running locally.
But how would I do it if say im on project 8857 and want to navigate to
url: “//localhost:3200/8857/”, instead.
When I simply add it to the path it doesnt load because the path seems to need to be the location I am running locally.