Thank you for your nice comment.
As for tempo, it reproduces the style of retro electronic music based on the clock. Therefore, you cannot freely set the BPM.
Just as there are strong restrictions on sound in 8-bit era, also it as such restrictions on tempo.
(Free BPM setting may not be impossible in the future, but now it is made with the above idea.)
The tempo number represents a division of the speed at 1.
The closer you get to 1, the rougher one step will be, so if possible, setting a larger number will bring the tempo closer. The length of the notes will be rough, but it may not be a problem depending on the song.