`gas_price` field of Contract call looks suspicious in state channels

[davidyuk]

I've called channels.get.offchain_state method of node and get this encoded call state tree:

cs_+QFBggJuAbkBOvkBNz8B+QEyuJf4lUABuEBRt/rxUTPwSp8BBMQWR70Ag6kTiNXTDmO2LWStsbEXhED9reWbZWfYmFIwTrKG6Khrbb7SvfC4T4ll2BtXsX/luE/4TSkCoQFZYYdOS6IFcvCPFPCBUOkebcCW0ZehLaMRA+K9RcniKwICoQVRt/rxUTPwSp8BBMQWR70Ag6kTiNXTDmO2LWStsbEXhAA9PwDAuJf4lUABuEBRt/rxUTPwSp8BBMQWR70Ag6kTiNXTDmO2LWStsbEXhADlKPCJlyMdCDQrNsajcRCzQk6M8LSJvbdnJ7Lc4aFjuE/4TSkCoQFZYYdOS6IFcvCPFPCBUOkebcCW0ZehLaMRA+K9RcniKwMDoQVRt/rxUTPwSp8BBMQWR70Ag6kTiNXTDmO2LWStsbEXhAEOVADAenqUfg==

Then I unpacked it and got two call entries:

'ba_Ubf68VEz8EqfAQTEFke9AIOpE4jV0w5jti1krbGxF4QA5SjwiZcjHQg0KzbGo3EQs0JOjPC0ib23Zyey3OGhY+BjbKc=': {
  callerId: 'ak_gN7nP72rm7D1kuSYWRtL9Sf4pFRoTPKM8wa9JHyneazW8zHm4',
  callerNonce: 3,
  contractId: 'ct_czPqotjcUujiXu5DaTeJMbv2WJpqwuhsQFn6edrGVRaoHLifk',
  gasPrice: '1',
  gasUsed: 14,
  height: 3,
  log: [],
  returnType: 0,
  returnValue: 'cb_VNLOFXc=',
  version: 2,
},
'ba_Ubf68VEz8EqfAQTEFke9AIOpE4jV0w5jti1krbGxF4RA/a3lm2Vn2JhSME6yhuioa22+0r3wuE+JZdgbV7F/5c9Ms1g=': {
  callerId: 'ak_gN7nP72rm7D1kuSYWRtL9Sf4pFRoTPKM8wa9JHyneazW8zHm4',
  callerNonce: 2,
  contractId: 'ct_czPqotjcUujiXu5DaTeJMbv2WJpqwuhsQFn6edrGVRaoHLifk',
  gasPrice: '0',
  gasUsed: 61,
  height: 2,
  log: [],
  returnType: 0,
  returnValue: 'cb_P4fvHVw=',
  version: 2,
},

In both entries gas_price is lower than a minimum gas price (1e9) and it differs between the similar calls, I assume it was generated on the node side. This field's semantic are probably different in state channels (is it nonce or round?), but I can't find related docs.

In this case contract call entries have version 2, but I can find documentation only for version 1 in https://github.com/aeternity/protocol/blob/c007dee/serializations.md#contract-call.