By the moment Ubidots just allows to their users visualize two decimals. The team is working to offer to the users an option to select more than 2 decimals.
Btw, looping in your question… I can note that your are sending the coordinates as a single value for each one “lat” and “lng”, is that right? The coordinates ought to be sent as context of a variable called position, gps, or location and the Ubidots backend will re direct automatically your device to the right place. For more information, you can reference to the Ubidots REST API Reference; also, the following article will serve you guide to send coordinates values to Ubidots.
All the best,