Issue with uptime figures for February 2023 minting receipts

[scottyeager]

There's a problem with minting receipts served by https://alpha.minting.tfchain.grid.tf/api/v1/ for the February 2023 period.

The uptime figures are way too large. See for example:

https://alpha.minting.tfchain.grid.tf/api/v1/receipt/0c828ff383bf9fd23eca2f95ba88c011e9da96849dbec626689f0d68beb5fab6

{
  "Minting": {
    "period": {
      "start": 1675366284,
      "end": 1677722920
    },
    "node_id": 1,
    "twin_id": 7,
    "farm_id": 1,
    "farm_name": "Freefarm",
    "stellar_payout_address": "GAL3ZIMKRDU2EJRFO7KX3YIMC7MIDDNQP5EKZWD6XI2DT6GOIBAUNYG7",
    "measured_uptime": 1.8445380626692141e+19,
...
}