Have a look at table-3 in this link.
The max is 8000 arp entry
The document is about NXOS release 5.1(3)N1(1)
But the footnote next to the ARP entry number says that 8K ARP entries is the max supported by NXOS 5.0(3)N2(1)
Maximum Limits—Indicates the maximum scale capability tested for the corresponding feature individually. This number is the absolute maximum currently supported by Cisco NX-OS Release 5.0(3)N2(1) software for the corresponding feature. If the hardware is capable of a higher scale, future software releases may increase this maximum limit.
So what is th emaximum for 5.1(3)N1(1)??