H1 Transfer with I-140

[manoj.engg]

Hi ,

I have a situation 

1- My I-140 is approved and my H1b expiring in 01/2019 (H1 Max out in 08/2019) 

2- I have go the new job from Y employer and they transferred H1 and got approval but only till 05/2019

Question i have

1- what could be the reason for short approval while i have approved I-140 ,shouldn't it be a 3 years approval  . or it does not depend on I-140 rather it depend upon job during in client letter and LCA

2- if i join new employer can they still use old I-140 for another extension (say 2 months after join ) or they  need to file PERM/I-140 before next extension.