Hasegawa 642 / F-90 - Where´s the mistake?

One question to Hasegawa´s recently reissued Ferrari kit.
They name it Ferrari 642 (F1-90) but correct me, if i´m wrong, 642 was 1991 not 1990.
For me there are two possibilities:
It is either a 641/2 - F90 with wrong starting numbers (as in 1990 there were Mansell [2] and Prost [1] ) or a 642 which would be a F1-91.

I´m confused, as i´m not an F1 specialist. What do you think?

http://www.hlj.com/product/HSG20239

Hi

It is the 642 from 1991.

Flemming

Thank you!