a whole two weeks

I spent a whole two weeks in Amsterdam.
I’m a little surprised about the above sentence because of ‘a’ before ‘weeks’, could you please explain it?

how to translate: ‘a whole two weeks’? - a period of two weeks?

Many thanks!!

It’s similar to “a period of two weeks”, but with more of a connotation that two weeks is quite a long time. So, the speaker is pleased, surprised, unhappy, etc. that he/she spent that long in Amsterdam.