نقل قول: Courses are compressed in the quarter system since a quarter is not as long as a semester. Where a semester is roughly supposed toe be 4.5 months long a quarter isn't but 3 months long. 
A good way to roughly figure that is a quarter hour is roughly equilvent to 2/3 of a semester hour. 
Like for example if a course is 3 semester hours in a school on the semester system. 
On the quarter system it will be roughly 2 quarter hours. It is all based on hours in the class room per week and total number of weeks. 
And in the 2 hour lab classes on the quarter system you'll just be getting about 1 1/2 or 1 1/3 hours credit. 

Problem of transferring and getting credit for all your hours comes in if you are planning on transferring schools and one school is on the semester system while the other school is on the quarter system. 

Some schools will convert them from quarter hours to semester hours for you and vise versa. Other schools won't. 

Example of that is two schools I know of one is on the quarter system. one is on the semester system. Both State schools requiring the same courses in each discipline to graduate 

For a degree from the school on the semester system it requires 157semester hours. 
For a degree from the school in the same course on the quarter system it requires only 120 quarter hours. 

Although both schools require the exact same courses for a degree. In the semester system school for those courses you will be getting 157 semester hours. In the quarter system school you will be getting just 120 quarter hours for the same courses. 

Like I said that is roughly the way to approximate the difference between quarter hours and semester hours. to be precise you will have to check with the schools to see exactly how they figure it. 
Hopes that helps.