How should I complete my METV application form for multiple trips to Thailand?

Hi all, I'm planning to do 2 trips to Thailand later this year being November to December for 6 weeks and then return in early January till early April. I have asked the UK Thailand embassy and they have told me to get a METV - Multi Entry Tourist Visa and the guidance note states the following shuttle h I don't understand. Can any body help me as I'm unsure when to complete the application form and what dates I should put on it..

The validity of the METV is 6 months from the issue which means you must enter before the ‘Enter Before’ date shown. The entry before the date is important because the last possible entrance for 60 days has to be used when entering the day before the end before the date. Two of the three 60 day exit stamps could possibly be extended for 30 days at a Thai immigration office although your last entry must be no later than the ‘Enter Before’ date.

Cheers in advance