sa-learn --dump magic

returns

0.000          0          3          0  non-token data: bayes db version
0.000          0        306          0  non-token data: nspam
0.000          0        210          0  non-token data: nham
0.000          0      68430          0  non-token data: ntokens
0.000          0 1318421928          0  non-token data: oldest atime
0.000          0 1319141693          0  non-token data: newest atime
0.000          0 1319142287          0  non-token data: last journal sync atime
0.000          0 1319142287          0  non-token data: last expiry atime
0.000          0          0          0  non-token data: last expire atime delta
0.000          0          0          0  non-token data: last expire reduction count

nspam and nham indicative the actual amount of learning and messages that SpamAssassin is using for its Bayesian analysis.