Thank you very much for your reply and explanation Abhishek. I started with ML just recently and looking for a way to get my head around it and dig deeper.
You mentioned TV and Newspaper. I completelly missed that our model is also using values for these. I though that we are working only with Radio and sales, since we are working only with those in dressData function. So, when I use 250 for input, and get y = 59.93558394326813 is amount of sale in thousands of units for our budget (250). Am I correct?