Glad you were able to get HDFview working, but I’m not sure it is useful for these data.
You are looking at a tiny piece of a large data set. For every hour there is a mapped array. In NASA Panoply you can enter the index (time axis) of an hourly array and get a nice image. The ERA5 NetCDF format is “experimental”, and some software complains that the “time axis” is not the first dimension (the first is a flag the differentiates between “production” and “experimental” data). The numbers you display appear to be the raw values. The metadata NetCDF offset and scale values. In Panoply these are applied, so you get pretty images with minimal effort.