Incorrect discount applied

Hi,

I have the plugin installed & set up a cart discount auto coupon for a flat rate $20 off over $100 spent.

The coupon is showing up fine but for some reason it is showing up a discount of $22 instead of the $20 which it is set for.

I have checked – it is not calculating a % and there do not seem to be any other issues. Simply it applies $22 (sometime $22.01) instead of the amount it should.

Site is http://www.1950sGlam.com and running the Blanco premium theme with Woocommerce version 2.4.7.

Love this plugin otherwise so please let me know if there is a fix.

https://wordpress.org/plugins/woocommerce-auto-added-coupons/