The standard +10 vet package costs 40 olives and contains 20 vets.
This package ur talking about is 11 x those 20 vets (hence the 10 + 1), and would normally cost 11x 40 = 440 olives. The package gives a reduction because of the amount ur buying, thus only costing 400 olives.

When you buy a +10 vet back for 40 olives you are actually getting 2 of them. Meaning 20 vets.

In this case, you are getting 10 (and a free one) for a total of 11. 11x10=110 vets. Multiply that by two and you are receiving 220 vets. Hopefully this clears it up for you. Please be aware that as you are getting a bonus free one in there, it is non refundable. In the end, using the deluxe pack ends up saving you olives compared to buying 11 vet packs.

this have same rules of use of normal ones? only if you have less 100 vets you can use this item?

They are no different than the normal items. It's a bundle of 11 of them for the price of 10.