fix: use number

pages/index/index.wxml

@@ -24,7 +24,7 @@
       </view>
       <view class="desc-text b-text ittflex-jcs">次健康早筛服务权益</view>
     </view>
-    <view class="btn default-btn buy-btn" bindtap="handlePackage">{{blanceCount == 0 ? '立即购买' : '立即预约'}}</view>
+    <view class="btn default-btn buy-btn" bindtap="handlePackage">{{useNumber == 0 ? '立即购买' : '立即预约'}}</view>
   </view>
   <view class="file-info">
     <view class="file-title">