The significant figures in the number 954.0509 are as follows:

The digits 9, 5, 4, 0, 5, and 0 are all significant.
The digit 9 is the first non-zero digit from the left, so it is significant.
The zeros between the non-zero digits (9 and 5) are also significant.
The digit 9 is the last non-zero digit from the right, so it is significant.

Therefore, the number 954.0509 has 7 significant figures.