One of the reasons why people use their fingers is to improve concentration since concentration is key to any act of worship
If you are counting your fingers, you are likely to concentrate more since it is easier to miss the number of repetitions you have in mind

After concluding every prayer eg fajr, immediately after making salaam (twice), we say Astagafiru Llah 3ce
There are other words of remembrance (dhikr) and supplication (dua) that we say
Some are said 3ce, 11ce, 33ce, 99ce. They are typically in odd numbers because Allah is one (odd number)
Don't let Mac scare you, the typical dhikr (remembrance and glorification of Allah)are usually around 11ce and 33ce
But Duas are usually said 3ce

If you have "Fortress of the Believers", you will find in it the details and their recommended numbers. Of course if you want to put Mac in his place, you can do thousands and tell him you did!

Although seriously, it is never right to boast about accomplishments in acts of worship
It is however perfectly ok to mention that you are doing this (eg 5 daily prayers) as a form of progress report, to encourage others and share ideas/suggestions for improvement

Allah knows best