L'indemnité de rupture?

> Is it 7 days pay, corresponding to the notice period?
Yes. I'd guess you are in a trial period?
.
> indemnité de rupture de contrat 5 (days) 188,83 (€)
188,83/day sounds OK (around 4000/month), and 5 days, as you probably don't work at weekends.
.
> why do they mention "prochain" salary
You'll get paid through the standard (next) payroll run at the end of the month.