C’ = C sharp maybe?
The slide parameter on the 303 is different than most other synths, since on the 303, you need to place the slide on the preceding note, on the A4, you need to place your slide on the note you want to slide to. You also need to adjust the Accent on the A4, since you can have it at differing values.
When looking at the 303 patterns on the website, you see a black dot, and a circle. These are your Note On and Sustain options. The A4 doesn’t have a “sustain note” option, so you need to input 2 of the same note, and tie them together with the slide.
Black Dot = Note On
Circle = Sustained Note
This might add to your confusion.