I've checked my btc address on a blockchain explorer. It says that the Total Receiving Balance is $100 but when i manually calculated every transaction manually via a calculator I've realized that the Total Receiving Balance is only $20 and I've spent only $10. The only thing that is accurate is the current total balance. Is there any explanation? I'm sure i have correctly counted my transactions.
Can you share which address you're using? That makes it easier to find the exact reason.
Some thoughts:
"my btc address": you could (and should) have more than one address.
"Total Receiving Balance is $100": Bitcoin doesn't count in dollars. Look at the Bitcoin amounts to be accurate. Blockchair.com for instance shows the dollar value when the transaction happened. So if you received 0.0025
BTC when it was worth $20, it will show $100 now.