Assuming a race without a pop bonus:
Base growth is 1.05
Every storm lowers that’s number with 0.05
Stack 8 storms and your growth will be
1.05 - 8x 0,05 = 0.65
In this case pop next tick = 0,65 x pop this tick.
For hypno 25 mill * 0.7 = 17,5 mill pop left in that tick you cast hypno. Tick after it can alrdy grow 800k.
Complicating factor. Pop planet, total pop on planet list, pop on hq and pop on player information run out of sync. Takes 3 ticks to stabilize. Cause for this is that some numbers update during, start or end of tick.