What are the overage charges for Serverless Function invocations

On the Netlify billing page the Serverless Functions
Invocations category for the PRO plan says

125k per site /month
($25+ when exceeded)

How is the additional $25 applied? For another 125k invocations?

If you scroll further down the billing page to the Per-site add-ons you can see the specifications/pricing for Level 0, Level 1, and Level 2

hi there, happy to clarify:

At the level 0 tier, a site (not team) has 125k function invocations. If this is exceeded, the site (not team) is bumped to Level 1 tier and has 2 million invocations. If this is exceeded, then we will charge for bundles of 500k invocation add-ons at $19 each.