That chart isn't correct. The numbers are identical for both year-to-date and January-only.
This may come of rude but I'm only being blunt. Year-to-date sales are of this year. This chart represents this year's January sales. Therefore, we have only been in 2018 for one month, which is January. Year-to-date sales will be the same, as it shows above, as the month of January. All of the cars listed above have the same January and year-to-date sales for 2018 since we have only had one month of sales reporting. Come February 28th or March 1st, the year-to-date sales and monthly sales will be different since year-to-date sales will cover two months, not just February sales.
If that doesn't make sense, you'll see once February sales are posted and we have another chart like the one above.