Photosynthetically active radiation (PAR) refers to the amount of light that plants get in your aquarium. Therefore, the higher the PAR the more light your plants have to use, but also the more light that algae has to use. It's all a balancing act between light, fertilizers, and co2 (if you have it)
Whether your estimated value of about 37 par is good or not depends on the plants you are using. 37 par is on the lower end, but if you are growing low light plants like anubias or crypts then that par value is fine.