How do we find out the length/timing of a vowel count while reciting Qur'an?

Question
How do we find out the length/timing of a vowel count while reciting Qur'an?

Assalamu Alaikum.  I am really confused.

I have read in your Tajweed answers that we cannot find out the vowel count of a letter, counting them on our fingers as this is not an accurate method.  For example if we are reading a word or verse in the Qur'an that is two, four or six vowel counts long, we cannot counts these on our fingers in a medium normal pace, as this not an accurate way to be measured.
For example, in Sura Naba, the first Ayah:  'AmmaYaTaSaaaaAloooon.  Can we count on our fingers four vowel counts for "Saaaa" and "Aloooon"?
Which way should we count the vowel counts for a beginner whether they are 2, 4 or 6 vowel counts long?
May Allah Reward you abundantly.

Answer
Wa alaikum assalaam wa rahmatullahi wa barakaatuh,
The matter is quite easy and insha' Allah not confusing at all.  One vowel count is the time it takes us to say a letter with a vowel.  For example: is one vowel count. If you multiply that by two, you get the timing of two vowel counts, which equals the time of:  , this is the same time as a medd letter, meaning equal to the timing when we read: .  Four vowel counts would be the timing of saying this twice e.g. .  
The timing for each vowel depends on our speed of reading, but the time of one vowel count should be consistent throughout our reading at each sitting, or section..  The is the reason why counting with our fingers is not a reliable method is that our fingers may move faster or slower than the actual vowel counts of our reading.  We need to develop an inner measure of our reading and multiply it out.  It will come naturally after a while insha' Allah. 
For the beginner, the teacher should point out that a particular medd is too long or too short and read the correct length for the student, so they can copy the teacher.  This will develop the inner measure to be accurate at all times. 
May Allah grant you the correct timing and ability to discern the correct lengthening count from the incorrect one.
Wa iyyaakum.
Wa assalaam