understanding Prefix-List

I am trying to understand the purpose of the number that comes after the "/".
example:
ip prefix-list TEST seq 5 permit 10.0.0.0/2 ge 17

2 means match 2 bits of first octet 10

however whatever I put , the prefix list will care just about the ge 17

to clarify it I have this table before filtering:

R1(config)#do sh ip route 
      10.0.0.0/8 is variably subnetted, 6 subnets, 6 masks
D        10.1.0.0/16 [90/156160] via 192.168.12.2, 00:00:01, FastEthernet0/0
D        10.2.0.0/17 [90/156160] via 192.168.12.2, 00:00:01, FastEthernet0/0
D        10.3.0.0/18 [90/156160] via 192.168.12.2, 00:00:01, FastEthernet0/0
D        10.4.0.0/19 [90/156160] via 192.168.12.2, 00:00:01, FastEthernet0/0
D        10.5.0.0/20 [90/156160] via 192.168.12.2, 00:00:01, FastEthernet0/0
D        10.6.0.0/21 [90/156160] via 192.168.12.2, 00:00:01, FastEthernet0/0

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if I use : ip prefix-list TEST seq 5 permit 10.0.0.0/2 ge 17
router eigrp 1
 distribute-list prefix TEST in

R1(config)#do sh ip route

      10.0.0.0/8 is variably subnetted, 5 subnets, 5 masks
D        10.2.0.0/17 [90/156160] via 192.168.12.2, 00:00:03, FastEthernet0/0
D        10.3.0.0/18 [90/156160] via 192.168.12.2, 00:00:03, FastEthernet0/0
D        10.4.0.0/19 [90/156160] via 192.168.12.2, 00:00:03, FastEthernet0/0
D        10.5.0.0/20 [90/156160] via 192.168.12.2, 00:00:03, FastEthernet0/0
D        10.6.0.0/21 [90/156160] via 192.168.12.2, 00:00:03, FastEthernet0/0

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so what 's the purpose of the number that comes after the slash sign "/", example:10.0.0.0/2

Thank you