Hi Valeria, st is an abbreviation of "Stone". It's one of unit of mass.

Hi. Estoy aprendiendo inglés...Saludos

'short ton': a unit of weight equal to 2000 pounds or 907.184 kilograms

Depending on context it could be 'stone' as in a measure of weight.

I've honestly never heard this before (I have basic investment knowledge) and Google wasn't much help either. My only suggestion is that it means $30 per stock, i.e. the stock price jumped by $30. People wouldn't normally write that though, as it's obvious that 'price' means 'price per stock'.