Changes in start date in BRP Card after changing to married name

[Nemo0115]

Hi,

My wife is due to apply her Tier 2 Genenral Visa this month. Upon completing the form online, she then asked "What is the start date of your current visa or leave to remain"? then the confusion happened. We got married here and updated her surname in her BRP card, so they took the old one and issued her a new one with new start date. My question is thus my wife need to put the old start date so it can be counted accurately in the future for indefinite to remain status or just follow the new start date given to the updated card which about 8 months less than the original start date given to her when she first entered in the UK. Thank you in advance. Happy new year to all.