How do I format my response in a custom Sensor Template?

Hello everyone, im currently trying to set up a REST custom sensor, which returns a json string. To read the json response I need to configure my REST template. My json response: {"diskusage":"50%","ramusage":"2246","cpuload":"7%","cputemp":"54.04"} My Template right now:

{
   "prtg": {
      "result": [
         {
            "Channel": "ramusage",
	    "CustomUnit": "gb",
	    "Float": 1,
            "Value": $.ramusage
         },
         {
            "Channel": "cputemp",
            "CustomUnit": "°C",
            "Float": 1,
            "Value": $.cputemp
         },
         {
            "Channel": "diskusage",
            "CustomUnit": "%",
            "Value": $.diskusage
         },
	{
	    "Channel": "cpuload",
	    "CustomUnit": "%",
	    "Value": $.cpuload
	 }
      ]
   }
}

Which works perfectly fine for my Integer/ Float values. But for "diskusage" and "cpuload" I get an error. Because value only accept Integers/ Floats but not string.

My Solution would be to cut off the "%" of the 2 values to "convert" it into a Float. But how do I do that? Is there any better way to do this?

api json prtg rest