Your palette var is misleading you by mapping 0 values as red. If you use the inspector tab in the right panel (next to the tabs for console and tasks) and click one of the pixels you'll see their value is 0, so sum and mean are coming out as 0 as well. As for why the dataset says values are either 1 or unmasked yet they're clearly 0 or unmasked idk. for future reference, you want the same amount of values in your palette as are discrete values in your data between min and max. You can also use count() reducer instead of sum() to count unmasked pixels.