I'm used to approaching this from the other direction (Y-DNA) so I'm not sure if I can answer. I will say that as far as I know it is not a numbers game - your haplogroup is determined by specific values for specific SNP(s), you either are or you aren't. I know my haplogroup from doing an SNP test at FTDNA, so when I first looked at my Promethease report I just saw the R1b... which is correct although it uses an older designation. However, I just went back and saw the I and Y (which doesn't exist, maybe they meant Y chromosome?) so I'm not sure what they are trying to tell you. The author of Promethease said in another thread that the focus was on medical and not haplogroups, so there could be some errors in how it is interpreted.
Typically you take a Y-DNA test which gives a series of markers called STRs. Your specific sequence of those markers is called your haplotype. Based on that, they can predict your haplogroup because other people with the same or similar haplotype have tested positive for some specific SNP(s). If you want to carry it further down the tree, you can get tested for whatever SNP is appropriate for your grouping.
I think the problem with ancestry DNA (and thus Promethease) is that the SNP picture as far as haplogroups is incomplete. For example, they may have tested 2 important ones but not a third, so you'll get incomplete or conflicting results. There will also be haplogroups that won't be represented at all. And as mentioned, it could simply be mistakes in their database.