Slice Tool in Photoshop

Hello good afternoon, I hope you are well. The reason for this doubt is because I am currently unable to resolve it. It's about the Slice Tool in Photoshop

Well I will try to explain myself, when I start making a file for WEB (the measurement is 1080 x 2160 px) and I use the Slice Tool to cut or divide my format into two equal parts (1080x1080px) I see that a new memory is made or a third Once I have moved out of my work area, I cannot remove or move this third box unlike the other two (1st and 2nd). But if I make another new file now in print mode with the same measurements (1080x2160px) and do these actions (use Slice Tool and divide the file into two equal parts) the tool works in the correct way because it only cuts two equal parts and It does not make me a third party.

makes sense? I add reference images. (The first photo is the WEB format and the second is a PRINT format.