I have a small group of students who are from Pakistan and we have a question for you. In their copy of the musHaf,... there is what they call a "waqfah"after the word "lakum"

Question
Assalaamu alaikum wa rahmatu Allahi wa barakaatuh,
May Allah reward you and all those whose efforts help us in knowing and applying to our lives what pleases our Lord.
I have a small group of students who are from Pakistan and we have a question for you.
In their copy of the musHaf,and they have confirmed that it is riwaayah Hafs 'an 'Aasim, that at aayah 36, surah Al Qalam there is what they call a "waqfah" ; after the word "lakum";. They said that it was "a stop longer than a saktah" but, when questioned they said it was not a waqf. I'm puzzled as I've never heard of it... Would you have any information about this? Jazakumu Allahu khaira.

Answer
Wa alaikum assalaam wa rahmatullahi wa barakatuh.
May Allah grant you and your students beneficial knowledge and give you all khair in both worlds. 
Although the word "waqfah" is not generally used, it has the same meaning as a stop.  Actually by definition, any stop longer than a sakt is a waqf (stop).  The tafseer changes with this stop, but is allowed and is present in the book on the stop and start called: Manaar Al Huda fee bayaan al-waqf wa-l-ibtidaa.  With stopping on "lakum" it would mean "What thing supports your claim?"  A question which shows rejection of what they claim. 
In conclusion, there is no special stop which is in between a stop and a sakt in timing in tajweed.  Those who stop on "lakum" in aayah 36 of Al-Qalam are making a regular stop,  which is allowed by the scholars as far as grammar and meaning. 
Wa iyyaakum.