1.In the SharePoint modern UI, when you fill in 6.5 in the number column, the real date (store in the SharePoint cloud) is 6.5. Due to the setting number of decimal is equal to 0, SharePoint automatically rounding decimal points of the value in the number column, so it displays 7.
But in the Power Apps, Power Automate and API, they get the real date in the number column, so the result displays 6.5.
2.Per my test, change the "number of decimal places" from 0 to Automatic will not cause the data lose. In the SharePoint modern UI, values in the number column returns 6.5.
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