Start_index and items_per_page not working for appointments

I’m trying to get the data about appointments, for example Im using python requests library to send GET request:

url to web page:

in the response from API I see 35 items from 45, so only results from page 1 as it shown on web page.
I tried to use parameters start_index and items_per_page, however the result from the api was always same (first 35 items) could you please help me to understand what I’m doing wrong?

for example I tried:
and so on, but I always get first 35 items in api response, please help.

I have just run
curl -u :

and got back the full 45 results
there is also some discussion here

that may help