Edit the wording on levels table

How can I edit the wording in the levels table? For example, change the “After your initial payment, your first payment is Free.” to say something like “Your first payment for this plan will charged to your account after the first 7 days.”. My clients say the wording is kinda confusing. See image as well: http://i.imgur.com/C2eqhHE.png

I have tried making changes to the following files, but no luck:

paid-memberships-pro/languages/pmpro.po
/paid-memberships-pro/includes/functions.php
/paid-memberships-pro/pages/levels.php

https://wordpress.org/plugins/paid-memberships-pro/