Your credit balance is your money. It should stay exactly where you left it until you decide to spend it, not shift around in the background because some matching system decided a job was relevant to you.
On Jobiteer, that's exactly how it works. Nothing gets deducted from your balance except the jobs you actually choose to unlock yourself.
Nothing gets deducted in the background
A job matching your specialty or service area doesn't touch your balance on its own. Matching is just information, it tells you a job might be relevant, it doesn't spend anything on your behalf.
You can watch your balance stay exactly where you left it
Check your balance in the morning, check it again that evening, and if you haven't unlocked anything, it's the same number. There's no quiet background activity to account for, no wondering whether something you didn't mean to spend on got deducted.
It's a deliberate action, not a side effect of matching
Every deduction traces back to a specific choice you made, unlocking a specific job. There's no ambiguity about where a credit went, because the only way one leaves your account is you actively spending it.
The bigger point
A balance you can trust to stay put is a small thing until it isn't. Knowing your credits are exactly where you left them, always, is part of what makes it easy to actually rely on the number in front of you instead of double checking it out of habit.