django-raster rendering raster url

[Xristos Xristoou]

i want to add raster functionality in django using postgis database using django-raster package and this docs http://django-raster.readthedocs.io/en/latest/tms.html

here my code :

models.py

from django.contrib.gis.db import models
class RasterWithName(models.Model):
    raster = models.RasterField()
    name = models.TextField()
add raster using console :

from django.contrib.gis.gdal import GDALRaster
from myapp.models import RasterWithName
gdal_raster = GDALRaster('C:/Users/username/Desktop/image.tif')
rast = RasterWithName(name='one', raster=gdal_raster)
rast.save()
but i am very confused with Rendering tiles and urls.

docs say :

/raster/tiles/layer_id/{z}/{x}/{y}.png where the layer_id is the primary key of a raster layer. This structure can be used directly in online mapping software such as OpenLayers or Leaflet. An example request could look like this: /raster/tiles/23/8/536/143.png, returning a tile in png format of the layer with ID pk=23 at zoom level z=8 and indexes x=536 and y=143

but indexes x,y mean some random x,y coordinate in image ?anyway i using this url http://127.0.0.1:8000/raster/tiles/1/8/536/143.png or http://127.0.0.1:8000/raster/tiles/1/8/20/40.png(origin x,y in my image) and i take a black window in my browser,any idea where i have wrong in my url rendering ?