Maybe i just understand mechanics of LA wrong but:
If i study chestnut 1st time my LA downed to 70%. Then i study chestnut second time and next chestnut should loose 50%. Then i studied wood chopping and my LA became 70% (for next chopping). After that i studied chestnut one more time and it gives me 70% exp, while it should give only 50%. This chestnut also decreased LA down to 35% like he was processed as 50%'ed.
I hope you understand me.