docs: clarify pbar in accept_reject sampler with batched conditions (#1493)

Author: StefanWahl

sbi/samplers/rejection/rejection.py

@@ -253,11 +253,6 @@ def accept_reject_sample(
 
     # Progress bar can be skipped, e.g. when sampling after each round just for
     # logging.
-    pbar = tqdm(
-        disable=not show_progress_bars,
-        total=num_samples,
-        desc=f"Drawing {num_samples} posterior samples",
-    )
     if proposal_sampling_kwargs is None:
         proposal_sampling_kwargs = {}
 
@@ -269,6 +264,12 @@ def accept_reject_sample(
     if "condition" in proposal_sampling_kwargs:
         num_xos = proposal_sampling_kwargs["condition"].shape[0]
 
+    pbar = tqdm(
+        disable=not show_progress_bars,
+        total=num_samples,
+        desc=f"Drawing {num_samples} posterior samples for {num_xos} observations",
+    )
+
     accepted = [[] for _ in range(num_xos)]
     acceptance_rate = torch.full((num_xos,), float("Nan"))
     leakage_warning_raised = False