20,000 Notifications...how to delete all at once?

Hello members…its been a while a came in here…I hope you are all fine!

I dont know how I ended up with 20,000+ notifications in 1 month…i want to delete all but XIBO CMS has delete limit of 100 notifications at a time…this will take me 9 months to clear

any short cut to purge all the messages in one command or how can i increase the list from 100 to 1000?