Update pixtral-12b-2409.mdx (#4424)

Updated limitations for Pixtral model regarding image size.

Author: fpagny

pages/managed-inference/reference-content/pixtral-12b-2409.mdx

@@ -160,7 +160,9 @@ Process the output data according to your application's needs. The response will
 Only bitmaps can be analyzed by Pixtral, PDFs and videos are not supported.
 
 #### Is there a limit to the size of each image?
-The only limitation is in context window (1 token for each 16x16 pixel).
+Images size are limited:
+- Directly by the maximum context window. As an example, since tokens are squares of 16x16 pixels, the maximum context window taken by a single image is `4096` tokens (ie. `(1024*1024)/(16*16)`)
+- Indirectly by the model accuracy: resolution above 1024x1024 will not increase model output accuracy. Indeed, images above 1024 pixels width or height will be automatically downscaled to fit within 1024x1024 dimension. Note that image ratio and overall aspect is preserved (images are not cropped, only additionaly compressed).
 
 #### What is the maximum amount of images per conversation?
 One conversation can handle up to 12 images (per request). The 13rd will return a 413 error.