Ryanair Weight and Balance
In order to maintain a 25 minutes turn around Ryanair uses a simplified loadsheet stating:
Rule 1: Mandatory: With 177 pax or less fwd rows 3 and 4 must be blocked
Rule 2: Optional: Both aft and fwd balance limits may be extended by 0,4 units for ZFW and TOW, provided:
a) No pax seated in the fwd 6 and aft 4 seat rows; maximum of 132 pax, or
b) 178 or more pax carried, or
c) Ferry flight (No pax)
Those rules makes it easy and very quick to board the aircraft, hope that gives you an explanation.