TCP actually starts with a large, random, 32-bit sequence number. Scapy appears to be showing you what the sequence numbers actually are. Wireshark is converting the TCP sequence numbers into relative sequence numbers. see TCP_Relative_Sequence_Numbers:
TCP Relative Sequence Numbers & TCP Window Scaling
By default Wireshark and TShark will keep track of all TCP sessions
and convert all Sequence Numbers (SEQ numbers) and Acknowledge Numbers
(ACK Numbers) into relative numbers. This means that instead of
displaying the real/absolute SEQ and ACK numbers in the display,
Wireshark will display a SEQ and ACK number relative to the first seen
segment for that conversation.
This means that all SEQ and ACK numbers always start at 0 for the
first packet seen in each conversation.
This makes the numbers much smaller and easier to read and compare
than the real numbers which normally are initialized to randomly
selected numbers in the range 0 - (2^32)-1 during the SYN phase.
This usability feature relies on features from
TCP_Analyze_Sequence_Numbers so in order to use this feature you must
also enable TCP_Analyze_Sequence_Numbers.
Using relative sequence numbers is a usability enhancement, making the
numbers easier to read and compare. In order to compare a dissection
with data from a less advanced analyzer that can not handle relative
sequence numbers it might be required to temporarily disable this
feature in Wireshark.
For Wireshark versions prior to 1.5: When the Relative Sequence
Numbers preference is enabled Wireshark will also enable "Window
For Wireshark 1.5 & newer: "Window Scaling" is a separate TCP
preference enabled by default.
If "Window Scaling" is enabled, Wireshark will try to monitor the TCP
Window Scaling option negotiated during the SYN phase and if such TCP
Window Scaling has been detected, Wireshark will also scale the window
field and translate it to the effective window size. This may affect
what the dissected and reported window is and may make Wireshark to
decode packets differently, but more accurately, than other tools.
To disable relative sequence numbers and instead display them as the
real absolute numbers, go to the TCP preferences and untick the box
relative sequence numbers.