Hi @Stream_biofilm, thanks for reporting this issue! It looks like Keemei isn't up-to-date with how QIIME 2 interprets metadata files coming from QIIME 1 (i.e. where the header starts with #SampleID). Right now Keemei will treat any lines starting with # as a comment, so it needs to be updated to notice #SampleID as a special-case QIIME 1-style file.
So with your data, Keemei is ignoring the header line (because it thinks it is a comment line) and treating the next line in the file as the header. This is why you're seeing an error about duplicate column names, since 7.3 is repeated in the second row.
You can safely ignore those errors. If you'd like to see Keemei successfully validate your file, as a workaround you could rename the first column to something like SampleID, and that'll also fix it (just drop the # character). But again, this is totally optional and won't affect how QIIME 2 interprets your metadata file.
I'm planning a Keemei release within the next few weeks to fix this issue and to make other updates to match QIIME 2's latest metadata file format spec. We'll follow up here when this bug fix is available in a Keemei release!