I was recently absent a day from work due to the flu.I usually stay back late hours and work. So I missed 8 hours that day I was absent but working two hours extra over regular work hours would see me make up those lost hours in 4 days. Would that count as me making up the hours for that day based on the extra hours I work?
It depends on who you ask, your manager or your HR representative.
( Speaking US here )
Most managers of salaried employees would be able to make that work if they wanted to, unless a specific HR policy prohibits this.
If your an hourly employee most likely that won't work and you will have to take a PTO day.
In short I would start a conversation with your manager to see if this arrangement is agreeable to them.
Would that count as me making up the hours for that day based on the extra hours I work?
The only way to know what "counts" and what doesn't is to ask.
Ask your manager, and ask whoever it is that manages your time within the company. You will be asking permission here - unless there's something in your contract, you aren't automatically permitted to "make up hours" this way.