In Diablo 3 you may have 13 tabs (not chests) at maximum.
Each chest contains up to 5 tabs.
So, if you have 10 tabs, you have 2 chests.
With 13 tabs, you’d see 3 chests (5 in first, 5 in second, and 3 in third).
What is it that you find hard to understand?
The only issue here seems to be a language barrier and because of it a misunderstanding of what the word “tab” means in this case.
I have full 13 tabs (since I have the necro DLC) and similarily as in the example pics posted by Boubou, there are 3 chests with 5 tabs in the first 2 chests and 3 in the last chest.
The thing that I find amusing is that OP had not played since S11, 2017 when Necro was introduced, and now wanted to complain that he was cheated out of “what he paid for”.
Six years of Seasons that could have given all the Stash Tabs.