Visual acceptance as per API1104

as per API1104 visual acceptance criteria for undercut is 50mm for continuous 300mm length of weld.what does it mean actually??upto 300 mm length of weld 50mm undercut accept?? or if the length is 350mm what is the acceptance level for undercut??

In any relevant area of 300 mm, allowed max. 50 mm in length of undercut.

our project 6 inch circumference of the pipe is 528.3 mm…if undercut comes for 60mm.will it be acceptable.??

Mean: (50 mm) in a continuous 12 in. (300 mm) weld length.
Reject: if your findings are 60 mm in any continuous 300 mm weld length.