回複：Does that mean

whenever you have a H1b, no matter it is expired or not, you can transfer your h1B or apply for a new H1b based on that quota at anytime?
-The H1 quote is limited to six years maximum. If you has used all six year H1, you need to go out of US for one year and then, you can get a new 6-year H1 quote unless you meet the requirement to extend your H1 beyond the six-year H limitaion.

If you do not use up all the six year limit, e.g. you used 4 years for your currrent employer, you can still use the left year, e.g. 2 years, when you do h1 extension or transfer.

My case is my H1b was expired in Mar. If now a new company wants to transfer my H1b, can they use this previous one or they need to apply for a new one as now this year's quota has not been used up?
- see above answer. You can not get a new quote.