This does not translate into using fingers for counting and addition!
As a grade one teacher, I spent a lot of time teaching my students to forget this habit. It was a difficult enterprise, and not always successful.
Do your child and yourself a favour, and use anything but fingers! There are lots of little items that please a child: plastic bottle caps, buttons, small lego blocks, pennies, etc. Your child can move these items around on the table, and the count isn't limited to ten items only!
I used bottle caps in my classroom to teach addition and subtraction. In my classroom, I used dominoes and dice frequently as well, and was absolutely amazed to see children using their fingers to add instead of counting the obvious markers: the dots!
The use of concrete items worked perfectly for teaching equations (for the number facts to 12). For example, the students had ten bottle caps and were instructed to write all the possible addition equations for the ten items. Of course, this was a final task after practising on the carpet with the class. We usually experimented with five caps each, and worked our way up to ten.
When the class had learned to build addition equations, they learned to move the bottle caps around to build subtraction equations.
They were essentially doing algebra! They could see patterns develop as they moved the caps around and recorded their discoveries. The ability to see patterns in numbers is a basic skill for learning math.
I encourage parents to discourage the use of fingers for math activities. Your preschooler will very quickly start to follow the first method that you choose to use.