There are no limit in input size. What is the input type you are using? We recommend to use a Local
CSV for large URL list instead "DIRECT" copy paste in setup.
Most recommended local input file format is TSV(TAB Delimited File) for better performance
When you have "Local file" option selected as a input type, Data Scraping Studio will check and read that file while execution and will add the entire URLs in queue and then start the extraction(See the logs message in below screenshot).
I just tested with a 800k+ URLs and all the URL queued in 8 seconds and scraping started without any issue.