[Not speaking on behalf of RG:]

The h-index in RG includes only citations from publications that were added to the database and if the citation format can't be handled by the RG algorithm, then you have bad luck.

In general, I discourage putting your h index on your resumé, but I discourage it even more for the values from RG. If you need to provide an h index, use on from WoS, Scopus or Google Scholar (and cite the source), although in one discussion here we also had an example of Scopus miscalculating as well.