I think 140 is a little less amount ammo considering the RoF
You are clearly not familiar with Anti aircraft gun systems...
The Shilka carries about 2,000 rounds of ready to fire ammo but each of the four cannon fire 1,000 rpm... meaning 30 seconds of ready to fire ammo.
Tunguska has a similar amount of ammo on board but each of the two twin barrel 30mm cannon fire between 2,000 and 2,500 rpm.
A paper rate of fire of 120rpm means 140 rounds would last more than one minute if it ever fired continuously... which it wont.
The barrel would melt and droop.
With modern fire control system and air burst shells and guided shells a shell or three would be fired and the results assessed... against many targets that would be enough.
Like the 2S31, the 2S38 seems also an artillery piece to export.
This is a high velocity anti armour gun, not artillery... and fitting it to a BMD chassis means airborne or naval infantry while its potential for anti aircraft use also suggests Aerospace Defence Force use too.
Ignore the vehicle chassis platform... we are talking about a new modular turret system for AA use or possible anti armour use or both.
This is potentially a new IFV turret, or a new SPAAG turret or possibly both... though I would expect the new SPAAG turret to have radar sensors too.