diff --git a/app/api/device_api.py b/app/api/device_api.py
index 6efe139..82c21f0 100644
--- a/app/api/device_api.py
+++ b/app/api/device_api.py
@@ -174,7 +174,7 @@ def list_all_devices_admin(request):
 
     page = int(request.GET.get('page', 1))
     page_size = int(request.GET.get('page_size', 20))
-    start = page * page_size
+    start = (page - 1) * page_size
     total = qs.count()
     items = [_serialize_device(d) for d in qs[start:start + page_size]]
 
diff --git a/app/services/payment_service.py b/app/services/payment_service.py
index c903434..ea37a00 100644
--- a/app/services/payment_service.py
+++ b/app/services/payment_service.py
@@ -136,7 +136,7 @@ class PaymentService:
         Returns:
             Decimal: 退款金额
         """
-        if refund_ratio < 0:
+        if not (0 < refund_ratio <= 1):
             raise ValueError(f'退款比例不能为负数: refund_ratio={refund_ratio}')
 
         amount = Decimal(str(paid_amount)) * Decimal(str(refund_ratio))
diff --git a/app/services/user_service.py b/app/services/user_service.py
index a039cf5..6b825b9 100644
--- a/app/services/user_service.py
+++ b/app/services/user_service.py
@@ -101,6 +101,6 @@ class UserService:
             qs = qs.filter(phone__contains=phone)
         if nickname:
             qs = qs.filter(nickname__contains=nickname)
-        if is_active:
+        if is_active is not None:
             qs = qs.filter(is_active=is_active)
         return qs