Hi tonialmeida,
Like Daermon, I too have "had access" to the FerroNATS offer and have spoken with them over the phone about the
vacaciones available. According to them, the 30
días naturales are 30 days of annual leave, not including your Off/Rest days. Therefore, for a 6-on/3-off cycle, you could theoretically have an annual block of 3+6+3+6+3+6+3+6+3+6+3 days off... not that that would normally be available in such a big block in practice, unless of course you apply long enough in advance..
The 30 days can be applied for any month of the year and don't, to my knowledge, need to be taken strictly in two blocks. Also, in Spain there are national holidays or
días festivos (such as Christmas day and the 6th of January),which vary between 12 and 14 per year depending on the region in which you work, and which are normal days-off for non-shift workers. If you are rostered to work one of these days, you allegedly (I say allegedly, as I have only been told this verbally and haven't seen it on paper) get an extra day of annual leave, or day-in-lieu, as compensation.
Therefore, if you're unlucky enough to be rostered for all 12/14
días festivos you should theoretically get 42/44 days of annual leave, not including your normal rostered off/rest days.
Hope this helps!