From the product description:
DirecTV HR10-250 HDTV TiVo (35-hours)
35-hours of high-definition recording, 225-hours of standard-definition recording.
In other words, your TiVo is showing correct information for a 250GB drive. For every hour of HD recording space not used, you have over six hours of SD recording space to use.
As for your other issue, call DirecTV and have them reset your channels; it should only take a minute or so.
TechLore Blog
HR10-250, Samsung SIR-S4120R, SIR-S4080R, 2 Philips DSR704s (one connected to a Slingbox A/V). One box used the "Zipper"; rest used PTVnet to enable networking features.
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