for some reason computing the mean in python and netcdfc++ gives two slightly different values

test_read.py

@@ -15,9 +15,18 @@ print("Shape of U:", U.shape)
 
 # Compute the mean of the variable across all axes (for all elements in U)
 U_mean = np.mean(U)
+U_sum = np.sum(U)
 
 # Print the mean
 print("Mean of U:", U_mean)
 
+print("Sum of U:", U_sum)
+
+masked_count = np.ma.count_masked(U)
+print("Number of masked values in U:", masked_count)
+
+nan_count = np.isnan(U).sum()
+print("Number of NaN values in U:", nan_count)
+
 # Close the NetCDF file
 ncfile.close()