Slurm sacct different two lines

Question

I have a question about Slurm sacct output.

       JobID  ReqCPUS    ResvCPU  AllocCPUS ResvCPURAW  SystemCPU CPUTimeRAW   TotalCPU    UserCPU
------------ -------- ---------- ---------- ---------- ---------- ---------- ---------- ----------
6089463_1          10   00:03:30         10        210  00:02.727       4250  06:38.627  06:35.899
6089463_1.b+        4                     4             00:02.727       1700  06:38.627  06:35.899

1. Why one job has two different lines?
2. Why 2 line has different ReqCPUS value? A user requests 10 CPUs but used only 4 CPUs?

Thank you,