Data downloaded from ECMWF is different from the sample data

I have downloaded ERA5 data following instructions on ECMWF. To check the accuracy of data, I downloaded data on 2022-01-01, just the same as the example data provided in [Google Cloud Bucket](https://console.cloud.google.com/storage/browser/dm_graphcast), but actually they were slightly different. Would I ask which API should be used to download these data, or could you publish a script or instructions for constructing input data?

Thanks a lot !