That’s revenue, their profit was $60B last year so it’s a pretty big fine. The payment is over a 10 year period though and roughly $5B out of the $18B is conditional, they only have to pay that of other companies like YouTube and TikTok don’t follow Meta’s lead on their changes:

• 2-hour daily cap, default across FB + IG, with warnings at 60/90 mins and 15-min nudges after
• Night Mode: blocked 12am-6am
• School Mode: muted notifications 8am-3pm
• No like counts visible to teens
• Ban on extreme makeup filters
• Stronger age-verification to catch under-13s and teens using fake adult birthdays