Your sales figures show you how much you have sold before any fees have been taken out (both PUSH fees & payment/payout processing fees).
For example, if you sell 10 products at $20 each, your sales will show $200.
Sales figures might also change due to refunds – you can read more about this here.
Your earnings are your sales minus payment/payout processing fees & PUSH fees; and will show you how much you have earnt from your sales.
You can see all of your earnings and balances in your Payouts page.
For more details about PUSH fees & payment merchant fees, head over to this article.