How calculate standard dev. in units for X spins ?

[synax.one]

Hello,

this is from nolinks://en.wikipedia.org/wiki/Casino_game:

SD (Roulette, even-money bet) = 2b sqrt(npq ), where b = flat bet per round, n = number of rounds, p = 18/38, and q
= 20/38.

For example, after 10 rounds at 1 unit per round, the standard deviation will be 2 x 1 x sqrt(10 x 18/38 x 20/38) = 3.16 units.

A: 3.16 is how many standard deviations?
B: Someone understand how construct this, please: 2b sqrt(npq )

Thank you, SYNAX

[synax.one]

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