Maximum stay of 180 days . 2 yrs long term family visit visa

[pkeshvani]

Hi There,
My mother in law has got 2 year long term visit visa.
She entered in UK in August 1st week and then went to europe for 2 weeks and entered to UK on 27th August returning from Europe.
1) how does "180 days max stay duration" works? does it count from her 1st entry from home country which was on 4th august or from the day she entered 2nd time which was on 27th august ?
2) once she leaves UK after 6 moths stay, can she return to UK againwithin 6 weeks period and stay here for another 5 months ?

I have read on internet and every post or forum states different things. some says about max 180 days stay during a rolling 12 months period. but this is nowhere mentioned on UKBA website!!
KINDLY HELP ME WITH YOUR SUGGESTION !!
MANY THANKS.

[vinny]

It's 180 days per entry or until expiry of leave, whichever is sooner. However, she may face questions to determine if she is a genuine visitor.