Changes in Accounting Estimates	12 Months Ended
Apr. 30, 2020
Changes in Accounting Estimates
Changes in Accounting Estimates	16. Changes in Accounting Estimates During the years ended April 30, 2020, 2019 and 2018, the Company revised its estimates at completion of various contracts recognized using the over time method, which resulted in cumulative catch up adjustments during the year in which the change in estimate occurred. The change in estimate was a result of the Company changing the total costs required to complete the contracts due to having more accurate cost information as work progressed in subsequent periods on the various contracts. During the year ended April 30, 2020, the Company revised its estimates of the total expected costs to complete a TMS contract and a contract associated with a design and development agreement. The aggregate impact of these adjustments in contract estimates on revenue related to performance obligations satisfied or partially satisfied in previous periods was a decrease of approximately $1,403,000 and an increase of approximately $1,099,000, respectively. The changes in estimates resulted in cumulative catch-up adjustments to revenue for the years ended April 30, 2019 were not material. During the year ended April 30, 2018, the Company revised its estimates of the total expected costs to complete a TMS variant contract. The aggregate impact of these adjustments in contract estimates on revenue related to performance obligations satisfied or partially satisfied in previous periods was a decrease of approximately $1,255,000.

Changes in Accounting Estimates

12 Months Ended

Apr. 30, 2020

16. Changes in Accounting Estimates

During the years ended April 30, 2020, 2019 and 2018, the Company revised its estimates at completion of various contracts recognized using the over time method, which resulted in cumulative catch up adjustments during the year in which the change in estimate occurred. The change in estimate was a result of the Company changing the total costs required to complete the contracts due to having more accurate cost information as work progressed in subsequent periods on the various contracts. During the year ended April 30, 2020, the Company revised its estimates of the total expected costs to complete a TMS contract and a contract associated with a design and development agreement. The aggregate impact of these adjustments in contract estimates on revenue related to performance obligations satisfied or partially satisfied in previous periods was a decrease of approximately $1,403,000 and an increase of approximately $1,099,000, respectively. The changes in estimates resulted in cumulative catch-up adjustments to revenue for the years ended April 30, 2019 were not material. During the year ended April 30, 2018, the Company revised its estimates of the total expected costs to complete a TMS variant contract. The aggregate impact of these adjustments in contract estimates on revenue related to performance obligations satisfied or partially satisfied in previous periods was a decrease of approximately $1,255,000.