you can use google translate (it is quite good) but basically they handled it so bad they ended up paying a 33 days instead of 20.
They tried to fire them without a reason which is not allowed in a Employment Regulation File (firing majority of the staff)
Mr musk had to sign personally due to the amount of money (1'6 mill) keep in mind that 'only' 24 of the 29 employess have been fired. So if each one would have gotten the same amount that would make 66.000€ per employee.
They did it so bad that if they ended up in the court they would have gotten “unfair dismissal”. That means the employee could choose between money compensation or get his job back.
They also got a payment due in stock options which musk tried to avoid, but it finally couldn't.
Also keep in mind spain has “pro worker” law but is not one of the most “pro-worker” countries in europe. The Scandinavian countries and france, as far as i know, are the ones who lead the way in this matter.