I'm not saying HB couldn't get this to work, but here's what he'd be dealing with:  {
.  "content": "!msg $[[0]]",
.  "inlinerolls": [
.  .  {
.  .  .  "expression": "[HR(20—(ceil((10)/1e10) + ceil((10)/4)))] 1D20",
.  .  .  "results": {
.  .  .  .  "resultType": "sum",
.  .  .  .  "rolls": [
.  .  .  .  .  {
.  .  .  .  .  .   "text": "HR(20—(ceil((10)/1e10) + ceil((10)/4)))", 
.  .  .  .  .  .  "type": "L"
.  .  .  .  .  },
.  .  .  .  .  {
.  .  .  .  .  .  "dice": 1,
.  .  .  .  .  .  "results": [
.  .  .  .  .  .  .  {
.  .  .  .  .  .  .  .  "v": 19
.  .  .  .  .  .  .  }
.  .  .  .  .  .  ],
.  .  .  .  .  .  "sides": 20,
.  .  .  .  .  .  "type": "R"
.  .  .  .  .  }
.  .  .  .  ],
.  .  .  .  "total": 19,
.  .  .  .  "type": "V"
.  .  .  },
.  .  .  "rollid": "—JbghwS——29c5v977dAJ",
.  .  .  "signature": "00a0ca795f48b2a499e0ac4d8ea0a2b4b1a9c8f8129ab12829ece6ac311d11f130a3631a182e8c8cc0d2d98a7b2f5d028c5df9091afb626864fd73146afcc100"
.  .  }
.  ],
.  "playerid": "—JS3qKxIUPHLzSbK24ve",
.  "selected": [
.  .  {
.  .  .  "_id": "—Jb8F8l1nGmAx9fWf8vU",
.  .  .  "_type": "graphic"
.  .  }
.  ],
.  "type": "api",
.  "who": "The Aaron"
}  Mathematical equations inside of labels are not expanded, so he'd have to pull that block and send it to the chat system to evaluate, then use the resultant number.