To calculate the total number of kilometers Dion ran during 28 days, you can multiply the distance he ran each day by the number of days:
\[ \text{Total kilometers} = \text{Distance per day} \times \text{Number of days} \]
Substituting the given values:
\[ \text{Total kilometers} = 3.75 , \text{km/day} \times 28 , \text{days} = 105 , \text{km} \]
So, Dion ran a total of 105 kilometers during 28 days.