To find out what value is high or not you have to understand what the item means. You could start by running 'strace -v netstat -s'. You'll find one of the keys it reads is /proc/net/snmp. This proc key showing traffic stats is populated by whatever goes on in the kernels source .*/tcp.c (around line 700-900 in kernel 2.4.9 IIGC). You'll find it's about in-flight SYN discrepancies. But what value would be high I wouldn't know, this shows on one of my machines:
7971661 active connections openings
7104573 passive connection openings
31224 failed connection attempts
and it definately works OK...