'C' is a constant, as in it never alters its value,
'V' is the speed or velocity of the space traveller,
V/C = is a ratio in itself.
A = the time spent in space travel. eg: 10 years.
T = the time experienced on Earth whilst this journey takes place. (also in years).
The following table shows how small differences in time dilation occur as a result of considerable increases in velocity.
To clarify the elements of the ATVC equation,
since C=Speed of Light which remains a constant at 300,000 KM/s.
you should measure this in KM/s so it relates to C as a comparative ratio,
but there is a simpler method as follows
If I travel at 150,000 KM/s which is half of the speed of light,
then V divided by C ( 150,000KM/s divided by 300,000KM/s ) is 0.5 in value.
I dont actually need to know the speeds themselves,
I can just substitute V/C as a decimal ratio of my speed ratio in relation to C (light speed).