An easy way around this not knowing you culture strength and it also helps your culture stretch farther , Is to make a starter Culture over night then use it at 1 to 1.5% of total make by weight .
To make it use 1/2 cup of fresh milk or powered milk and add 1/32 tsp to it and mix well then leave overnight or up to 24 hrs in a warm place , ( I use oven light ) when the curd a whey seperate into layers and or it taste tangy it is ready to use as mentioned above .