installed port wants to rebuild

[Stan Sanderson]

OS X 10.14, all installed ports up-to-date.
Re: kmymoney4-devel

Since the recent problem with kdepimlibs4 was solved (thanks!),  port upgrade outdated consistently ends with
--->  Scanning binaries for linking errors
--->  Found 2 broken files, matching files to ports      
--->  Found 1 broken port, determining rebuild order
You can always run 'port rev-upgrade' again to fix errors.
The following ports will be rebuilt: kmymoney4-devel @4.8.1-20171206

port installed kmymon* returns
   kmymoney4-devel @4.8.1-20171206_2 (active)
and, indeed, it is running normally. However, I’m wondering where the “_2” came from, why I am prompted to rebuild each time, and how to correct it.

Thanks,

Stan