Using variables in scripts

Hi, I’m extremely new to WorkFusion and to RPA and I was wondering if this is allowed:

I found this mail script online and I want to use variables in there so I simply just did this:

<?xml version="1.0" encoding="UTF-8"?>
<config xmlns="http://web-harvest.sourceforge.net/schema/1.0/config">
	<mail smtp-host="smtp.gmail.com" 
		smtp-port="587" 
		type="html"
		from=from
		to=to
		subject="Some entity thresholds were not reached"
		charset="UTF-8"
		username=email
		password=password
		security="ssl">
			Hi there, 
			This is your Metamaze upload report:
			Some entities were not extracted with a high enough certainity threshold : + uncertainEntities + .
			We recommand you go check it Out.
			The Metamaze Team  
	</mail>
	<export include-original-data="true"></export>
</config>

where email, password, from and to refer to variables that I have made in the Recorder Variables tab
Also, I would love to use a variable (uncertainEntities) inside the body of the mail.