I went to @bubyduby007's mechanic, Mr Moin ex Iqbal Autos, F-10 Markaz.
He open the transmission chamber, drained out the oil, cleaned the filter, replaced the chamber gasket, screwed it back and then used some kind of oil pump to fill in the oil .. To my surprise, the transmission took all 6 liters of oil ....
I was really tense on my way back home, worried about the possibility of an overfill, but nothing happened and the ride was as smooth as can be.
As per Moin sahib, when these JDMs are despatched to Pakistan, oils aren't topped up and when transmissions are drained, only that much oil comes out that is left in the transmission over the tenure of running. Thence, mechanics usually fill up with 3-4 litres of oil, not knowing that the transmissions can take more oil ..
That's the story up till now ..