[Vocabulary] Matrix?

[njt2009]

If on said he could remember a matrix of 50 digits.
What does it mean? Is it mean 50 numbers in total or 50x50 =2500 numbers?

 

[Raymott]

If on said he could remember a matrix of 50 digits.
What does it mean? Is it mean 50 numbers in total or 50x50 =2500 numbers?

No, a matrix of 50 digits has 50 single-digit numbers, eg. a 5 x 10 matrix, assuming that's the kind of matrix meant. You're describing a "50 by 50 matrix of digits".