90 Day visa

[c.g]

A friend has just help my nan get a 90 day visa she arrives in Thailand on the 1st of dec till the 1st of feb, however the visa is dated 20th October-20th Jan is this a time where it needs to be used and 3 months will be given on entry or is the visa valid until the 20th Jan??

What options do we have if it's only valid until 20th Jan

Thanks in advance

[dtaai-maai]

She must arrive before 20th Jan and will then be given permission to stay for 90 days.