Please tell me whether I understand the following two sentences correctly:
1-He will be back in thirty minutes.
2- He will be back within thirty minutes.
Suppose now is 1PM. The first means he will be back sometime after 1:30PM; the second means he will be back sometime before 1:30PM.
Now for something past tense:
1--He established a charity fund in 1990. In just ten years, it raised ten million dollars.
2--He established a charity fund in 1990. Within just ten years, it raised ten million dollars.
Do the above two mean the same for 'in' and 'within'? Thank you.
"He'll be back after about 30 minutes" means he'll be back sometimes shortly after 1:30.
In just ten years -- it's clear that you mean that in the ten years combined, the total amount raised was $10 million.
Within ten years -- you might use this to show how quickly something changed.
He established a charity in fund in 1990, and the first year it raised $2 million. Within ten years, it was raising $10 million annually. (It took only 10 years to achieve this huge increase.)
It can go the other way too.
When John Smith played his last game of baseball, he was earning $16 million a year, and had been for the past three years. Yet within five years, he was broke and living with his brother. (It took only five years for him to spend all that money.)
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.