Calculating FIT for Magnetic Sensors
There are many on-line calculators you can use to get the MTBF from your data. One example is: https://reliabilityanalyticstoolkit.appspot.com/field_mtbf_calculator. Using your data at this site yields the following results: at 60% confidence, MTBF = 87,309 hr and a failure rate of 11 per million hours (since FIT is for 1 billion hours, the FIT would be 11,000). For 90% confidence, the results are MTBF = 34,744 hr and a failure rate of 29 per million hours (FIT of 29,000). The formulas and rationale for them can also be found on thus site (they are too complex to include in this answer).