Inspiron 15 5577 Storage configuration

I just want someone to confirm that if I use an SSD and a 1TB hard drive, I can only use a 128GB SSD? Specs says SSD can handle up to 512GB however it can only be 128GB if I have a hard drive too. Can someone please confirm this for me? I do not want to buy a 512GB SSD if I can't use it together with my 1TB hard drive.

https://www.dell.com/support/manuals/en-ie/inspiron-15-5577-gaming-laptop/inspiron15_5577_setupandspecs/memory?guid=guid-75c3ed1c-1bb5-4c43-854d-648447036c7b&lang=en-us