Hostnamebindings error and how can we solve it ?

I am unable to find it necessary information in this template about hostnamebindings
https://github.com/Azure/azure-quickstart-templates/blob/master/201-web-app-github-deploy/azuredeploy.json

**### Issue Details**
When I try to deploy an arm template I am getting this error.,

**Error in Powershell**
New-AzureRmResourceGroupDeployment : 17:09:29 - Resource Microsoft.Web/sites/hostNameBindings 'monitorfunctionswivpj9/monitorfunctionswivpj5hlzdq3i9.azurewebsites.net' failed with message '{
"Code": "BadRequest",
"Message": "Too many (2) hostnames in the default DNS zone. Limit is 1.",
"Target": null,
"Details": [
{
"Message": "Too many (2) hostnames in the default DNS zone. Limit is 1."
},
{
"Code": "BadRequest"
},
{
"ErrorEntity": {
"ExtendedCode": "04017",
"MessageTemplate": "Too many ({0}) hostnames in the default DNS zone. Limit is {1}.",
"Parameters": [
"2",
"1"
],
"Code": "BadRequest",
"Message": "Too many (2) hostnames in the default DNS zone. Limit is 1."
}
}
],
"Innererror": null
}'

**My resources section**

{
"comments": "Generalized from resource: '/subscriptions/1f2dbbd7-69f6-443f-961f-988dbc9ee66a/resourceGroups/logicApps-rg/providers/Microsoft.Web/sites/monitorfunctions/hostNameBindings/monitorfunctions.azurewebsites.net'.",
"type": "Microsoft.Web/sites/hostNameBindings",
"name": "[concat(variables('functionsname'),'/', variables('hostnamebindingsforfunctions'))]",
"apiVersion": "2016-08-01",
"location": "East US 2",
"scale": null,
"properties": {
"siteName": "functionsname9",
"domainId": null,
"hostNameType": "Verified"
},
"dependsOn": [
"[resourceId('Microsoft.Web/sites', variables('functionsname'))]"
]
}

**My Variables Section**
"variables": {
"hostnamebindingsforfunctions": "[concat('monitorfunctions',uniqueString(resourceGroup().id),'9','.azurewebsites.net')]",
"functionsname": "[concat('monitorfunctions',substring(uniqueString(resourceGroup().id),0,5),'9')]"
},

**### Repro steps (*if necessary, delete otherwise*)**
1. run this using powershell
2.send command .\Deploy-AzureResourceGroup.ps1 -ResourceGroupLocation ukwest
3.The resources created
4.But there is an error in the background

Start with 201-web-app-github-deploy/azuredeploy.json and the Deploy-AzureResourceGroup.ps1 entry point, then reproduce the deployment with the PowerShell command in the issue. Inspect the Microsoft.Web/sites/hostNameBindings resource and its variables against the reported hostname-limit error. Done means the template deploys without the background hostname binding error.

Written by the indexing model from the issue text.