Get a Property, a Counter, and a Text.
Set the Property to [numbers] and default value to 0, you will need this to update the value of counter inside of Text.
Set the Counter to [not visible in game], and make it display the Property device you have placed earlier.
Lastly, inside of the Text, find Blocks option and create a block when receive on a channel, this channel should be the one that increases/decreases the counter value.
Insert this block code inside the Text:
Set text - Create text with - Get property - [Property]
You might also want to switch the topic category to Help.