Bhutan coins

Can someone, please, explain me this. In Bhutan "Bhutan - Rupee (decimalized, 1957-1974)" starts from 1928. How could it be, if here is written from 1957 to 1974?
https://en.numista.com/catalogue/bhoutan-1.html#devise474
Regards
Kuna

I do not know the answer, but I can speculate.

It is possible that the currency existed a long time before coins were struck.  Perhaps Bhutan used paper money alone until the 1950s.

India decimalized in 1957, and the Bhutanese rupee was linked to it.

I can only speculate that Bhutan started using non-decimalized rupees from 1928.

But then the coins minted in 1928 are in the wrong coin section.
Please, if someone can change that.
Regards
Kuna