sequence numbers

hi,

ive capture a http download with: tcpdump host x.x.x.x -c 100

wireshark shows me these sequence numbers for the first 5 packets:

0
0
1
1
1

but tcpdump shows:

1636902786
1161722083
1
1:192
1

tcpdump -vvr http-download.pcap | sed 's/1.2.3.4/myprivateip/g' | head -10

reading from file http-download.pcap, link-type EN10MB (Ethernet)
21:26:33.318368 IP (tos 0x0, ttl 64, id 64732, offset 0, flags [DF], proto TCP (6), length 60)
    myprivateip.32773 > zinc.canonical.com.http: Flags [S], cksum 0xa467 (incorrect -> 0x8522), seq 1636902786, win 14600, options [mss 1460,sackOK,TS val 14211934 ecr 0,nop,wscale 4], length 0
21:26:33.338102 IP (tos 0x20, ttl 48, id 0, offset 0, flags [DF], proto TCP (6), length 60)
    zinc.canonical.com.http > myprivateip.32773: Flags [S.], cksum 0x7c95 (correct), seq 1161722083, ack 1636902787, win 5792, options [mss 1460,sackOK,TS val 2713111304 ecr 14211934,nop,wscale 7], length 0
21:26:33.338119 IP (tos 0x0, ttl 64, id 64733, offset 0, flags [DF], proto TCP (6), length 52)
    myprivateip.32773 > zinc.canonical.com.http: Flags [.], cksum 0xa45f (incorrect -> 0xbe6b), seq 1, ack 1, win 913, options [nop,nop,TS val 14211939 ecr 2713111304], length 0
21:26:33.338252 IP (tos 0x0, ttl 64, id 64734, offset 0, flags [DF], proto TCP (6), length 243)
    myprivateip.32773 > zinc.canonical.com.http: Flags [P.], cksum 0xa51e (incorrect -> 0xdcad), seq 1:192, ack 1, win 913, options [nop,nop,TS val 14211939 ecr 2713111304], length 191
21:26:33.358015 IP (tos 0x20, ttl 48, id 46062, offset 0, flags [DF], proto TCP (6), length 52)
    zinc.canonical.com.http > myprivateip.32773: Flags [.], cksum 0xc105 (correct), seq 1, ack 192, win 54, options [nop,nop,TS val 2713111306 ecr 14211939], length 0

whats with the difference?

offtopic, but you guys probably know it anyway: ive looked at python-scapy but have had some problems, are there other good python ways to read .pcap files?